Sorry to hear/see you're having issues with salt prints
@ajmiller, but don't feel bad about it - it's a deceptively simple process. Emphasis on 'deceptively'! The prints are gorgeous if they come out nicely, but it can take some work to get from "hey, I've got an image" stage to "this is actually a good print."
I'd suggest the following troubleshooting process:
1: Ensure that your process works and is consistent. Print the same thing (doesn't matter what) with the same parameters 3 times or so. If you get identical prints, that's a good sign. Be sure to mask a sensitized part of the paper with something that's perfectly opaque to UV during exposure (rubylith or lithographer's tape usually works OK). This masked part should come out paper white. It helps if this masked part covers a sensitized part of the paper and an adjacent unsensitized bit, so you can compare actual paper white (unsensitized) to sensitized, masked white. If you see a noticeable density on the sensitized but masked part, you have fog and your process is not under control. Fix this before proceeding. Also do a test for maximum density by deliberately overexposing a strip of sensitized paper. Put it in direct summer noon sun for half an hour or so (no glass cover etc.) and process it. This strip should come out (after drying) a satisfying very deep chocolate brown-bordering-on-black (measured density above 1.2logD if you happen to have a reflective densitometer - if you don't, just go by what your eyes tell you). If the black turns out grey or pale, your process is not under control and there are problems to fix. Ensure that you get a good evenness and no coating defects (streaks etc.) Change your coating/application methods if you have any problems with unevenness.
2: Establish the exposure time for proper dmax. Forget about negatives, step wedges etc. at this point. Just print a sensitized sheet/strip in your contact printing frame. Make a stepped exposure by covering part of the strip with a piece of card and moving that piece of card to make different exposure times. Try times in an exponential series: 1 minute, 2 minutes, 4, 8, 16, 32. You should see density increase in more or less equal steps. At some point, you'll notice that increased exposure does not yield additional density. The last exposure that gives a significant increase in density is a good base time to go with. Note that this exposure does not yet account for the base density if your film. You can do this same test with a blank sheet of film (inkjet or camera film, depending on what you use). If you use camera film, ensure the blank sheet is unexposed, but
developed and fixed. Development is important because it can add a small amount to the base density. When judging densities, do so on processed, dried prints/strips. Ignore the density you see during the process; it's deceptive.
3: Now print a negative and/or step tablet (I like the Stouffer T2115) with your base exposure time. If you determined that time using a blank sheet of film, then use that time. If you determined the time without film, so just the paper in the contact frame, I'd recommend to do some tests with small increments, e.g. 2, 4 & 6 minutes on top of the base exposure time. This is to account for the additional density of the base. This test will tell you what the density range of the process is. You'll notice that your salt prints will show differentiation between the 0 density step and ca. 2.30logD (or even a little more) on your step tablet, with the highest densities being paper white. You can now proceed to make negatives (inkjet printed, camera negatives) with the proper density range to get a full-scale print.
4: Verify your negatives; I personally like to work on 4x5" for this when using camera negatives. Make a suitable (as best you can) negative and print it side by side with a step tablet using the exposure time you've established before, and be sure to mask at least one sensitized edge to check for fog. Verify that the blacks are OK, the whites are clear and the negative indeed occupies the expected tonal range. If the image comes out too dark,
do not be tempted to expose the print shorter but fix the negative (make a new one or chemically intensify it). In principle there's nothing inherently wrong with underexposing your prints, but the results will virtually always be lackluster and disappointing. You'll realize at some point it's a waste of time trying to 'fix' prints from weak negatives. On the other hand, if your print comes out too light, you can try increasing exposure, but you'll likely lose some shadow detail. So you're balancing on a knife's edge if you want to make a really good print. Don't worry though - as it turns out, it's a pretty blunt knife and there's plenty of room to balance on it. If your print comes out with the proper tonal range, but the shadows are too blocked up, you'll need to expose the image (in camera) longer and maybe adjust development (a little shorter) to get the same tonal range.
If you're working with inkjet digital negatives, your linearization/calibration process takes place after step 3
and not earlier. Linearizing a process that's not demonstrated to be in control is a waste of time.
So much for the general stuff. Coming back to your actual print, a few remarks:
* Two parameters are missing from your description: how much salt (sodium chloride) is on your paper and how you expose the print (type of light source, power, distance + exposure time). It's very hard to say anything sensible without knowing these two parameters.
* I'm asking about the salt (chloride) specifically because your prints looks remarkably neutral in tone. Untoned salt prints are virtually always a lot warmer in hue. Getting this cool tone with low density can be indicative of either too much or too little chloride to go with your silver. The ratio of chloride to silver is absolutely critical for getting optimal results. Again, this is a blunt knife so there's a certain bandwidth that turns out to work OK (with some contrast and hue variation in this bandwidth), but you need to hit it fairly exactly to get good maximum density. Too much salt as well as too little salt will both result in low density and flat prints. I personally use an 11% silver nitrate solution and 1.6% sodium chloride; both applied in equal amounts; a 4x5" print takes me ca. 0.75ml of each to fully coat (with a margin), but this depends strongly on the absorbency of the paper.
* I prefer to brush-coat the paper with a measured amount of salting solution, then dry, then either brush- or puddle-pushing coat the paper with the silver nitrate solution (again a measured amount). I find this gives good control (and consistency!) over how much salt and silver actually end up on the paper. Methods involving floating can work well, but can also induce problems in this regard under influence of environmental parameters like moisture content of the paper, paper type, temperature etc. I've never found the addition of a wetting agent (Tween, Photoflo) to help any and in fact I've only seen it make matters worse on papers that somehow protest against being printed on. YMMV.
* Fomapan 100 is a fine film for salt prints (I've used it for several years, also for salt printing). I've not developed it in HC110 so I can't reflect on that other than that I think you should be in the ballpark with your ca. 2x development time compared to normal development for silver gelatin printing. Your negative does look underexposed judging by the lack of separation in the shadow areas. You may want to rate this film at EI50 and when metering the scene, ensure that no important shadows end up at lower than -1.5 to -2.0 stops. I find that a properly exposed salt print works well with a negative that has fairly robust shadow separation.
Given the remarks above, I expect that your work for now is in step 1: getting the printing process to work in the first place. I'd not worry about negatives for now, and focus on getting a good dmax.
As you may have realized, everyone has their own ways of doing this and one way is not inherently better than another. As long as you're getting good prints, what you're doing is evidently right. Until you reach that point, take inspiration from anyone and everyone, and happily borrow & steal tricks & procedures that make sense to you. Try to experiment systematically to find what works for you, and always try to explain the problems you run into. An unexplained problem is more often than not one that'll bite you in the behind sooner or later, even if it seems to go away all by itself.
Years ago, I made this video of how I did the process at that time; generally speaking I still work in the same way, although I prefer to brush coat instead of puddle-push as long as I get good evenness that way.
Also have a look at
@Andrew O'Neill's videos; you'll notice he does things differently from how I do them (and we probably both deviate from Ellie here and there). Again, none of us is right or wrong; we just do what we have determined works for us.