As others have said, it is best to use tests for residual silver and hypo to test your particular workflow.
There are a couple of things to be aware of along the way. I'll address your questions one-at-a-time.
I wonder if I fix and wash my fiber prints long enough.
Can I, after running a test strip through the below process, just put it back in developer and see if it darkens?
If there was any silver left on the paper shouldn't that get dark in the developer then?
How do I test for residual fixer?
Fixer changes silver halides into soluble compounds that can be washed out through a number of intermediate steps. The intermediate compounds are insoluble but not light sensitive. In other words, if these remain in the paper or emulsion due to inadequate fixing, they won't develop out when exposed to light and placed in the developer. However, a test for residual silver like the Kodak ST-2 or the selenium toner tests mentioned above, will show them. So, use a proper test. The instructions for the test are found in the linked-to posts above but basically, you put a drop of test solution on a clear white part of a print or test strip and see if the spot discolors. Only a very faint discoloration is acceptable; no discoloration is preferable. Do research the correct testing procedure for the method you choose. FWIW, I like the selenium toner method since I have toner on hand always.
If the stop bath stops developing completely, can I turn the lights on in the stop bath?
Theoretically, yes. And you can then fix (in an acid fixer) and wash the film or paper and watch it clear in the fixer; a great learning experience if you haven't done it.
However, be careful when fixing with the lights on if you use an alkaline fix. Developer is only stopped in an acid stop bath and the carried-over developer can be reactivated in an alkaline environment. I know this from personal experience; i.e., fogged negatives from turning on the lights to early in TF-4 fixer. Don't try this with your Moersch alkaline fixer!
- Dektol 1+2, 2 mins
- Ilford Stop bath, don't time this, maybe 10-30 seconds
- Quick water rinse
- Moersch Alkaline Fixer, 1 min
- HCA, 2-5 minutes, I don't really time this
- Paterson print washer, 30 mins
A couple of comments about your processing work-flow:
First, stop for 30 seconds minimum.
Next, a water rinse before most fixing baths is unnecessary. Even alkaline fixers are formulated to be used with a stop bath (Moersch sells a citric-acid stop). Check the product instructions to be sure. I think you can eliminate a step and save some time.
Be aware when using short (1 minute) fixing times and strong fixers with fiber-base papers (a lá Ilford) that the capacity of the fixer is rather small. If you are processing for optimum permanence, it is only about 10 8x10 prints per liter of fix. Commercial standards (or general-purpose standards as they are also called) gets you up to 30 8x10s or so per liter, but not processed to "archival" standards. A more economical approach is two-bath fixing. Do some research on this if you are interested. Just keep in mind that if you are processing 30+ 8x10s in a liter of fix one-bath that the last 20 are less-than-optimum-permanence.
If you use HCA, be sure to agitate! Times vary by manufacturer; Ilford recommends 10 minutes for its archival sequence, Kodak only 3 minutes for double-weight fiber-base paper. There are different processing strategies at work here: Ilford uses the longer wash-aid bath to reduce washing times, Kodak relies on a longer wash. FWIW I use the longer times for both steps.
Washing time depends on your water, the temperature and how long you have fixed (i.e., how saturated the paper base has become). Therefore it is really best to test your specific workflow. Get the HT-2 test kit and do a test run, pulling test strips from the washer starting too early and then at regular intervals till you get an adequate wash. Then you can add a generous safety margin and be confident your prints are being washed adequately. Personally, I like 60 minutes.
Best,
Doremus