I think you need to reframe how you think about this, I know I had to when I started with studio work. It helps to think about the whole process.
When shooting in natural or existing light we measure (meter) to see what's there and then adjust the camera to expose to get a negative "that we can work with". Then in the darkroom we have to adjust for contrast and burn and dodge and blah, blah, blah, to get subject matter on the print where we want it.
In opposition, a pure artificial exposure (typical studio lighting) is "set" to the camera setting we want, the contrast we want, the placement we want. We adjust the scene lighting rather than adjusting the camera, adjusting the enlarger, burning, dodging...
When the lighting is designed from scratch to fit the camera settings the exposure can be perfect for everything in the scene. A successful artificial light shot straight prints without any extra work. Standard enlarger settings, no burn, no dodge, standard paper...
So, when designing a studio setup, you start by choosing the film, the aperture setting, and the shutter speed.
You make these choices (first) based on the characteristics you want, then (second) based on practical concerns. Practical concerns might be that your lights aren't powerful enough to expose ISO50 film at f/16, there are other practical limits you'll bump into.
Once you have the film, aperture, and speed set you start playing with the lighting until everything in the scene will expose properly.
When setting the main lighting for the face the meter goes "at the subjects nose" and with dome retracted pointed at the main light, your 45 degree angle. (Side note; the main light doesn't have to be pointed straight at the subject. It's position may be "on a 45" from the subject but turned/feathered "at a 80 or a 10" to the camera shooting line.)
To measure the fill light on the off side the meter head is turned toward the foam board (turned away from the main light but still held at the subjects nose), with the dome retracted the meter then can't see the main light, so you can get a measurement of just the fill; the bigger the difference, the bigger the contrast. If there's too much contrast move the foam board closer to the subject, or vice versa. (Side note; sometimes the light and reflector may need to be very close to the subject, as in just outside what the camera can see.)
At this point the only thing that is setup to properly expose is the subjects face.
The next step is to measure what's happening in the rest of the scene. Measure the background; too light or dark feather or move the main light to fix it. Measure the left boob and right hip or whatever and tilt the lights or feather the foam board or ... until its right.
Now recheck the overall set with a dome out pointed at the camera reading; it may indicate slightly different that the direct main light reading but should be close. (Side note; this step is more important when you are using multiple lights.)
At this point you've put in a fair amount of work. Grab a tape rule, sketch out your set with measurements and settings... You can then duplicate it very quickly.
After all that work what you end up with is a "set" that will produce a remarkably consistent result, you get a nearly perfect result with every shutter fire.
After some practice you also understand whats happening so you can adjust the look you want very quickly.
Metering in studio during a shoot is just to make sure you have the "set" done right and that the lights are working, not to set the camera.
