Hey Tatty,
I understand your frustration.
The first thing I'd suggest is picking one time to use for developing your paper. Use a time that assures you can get strong blacks and use it every time. (This removes a variable for now. Later on when you get the rest figured out you can play with the developing time as a fine adjustment.)
The next thing to understand is the concept of place and fall with regard to exposure of photographic materials. You only get to place one tone, say black, with any single exposure. If you place black the rest of the tones just fall where they fall.
When you do your test strip pick the time where say, in your example, the shadows in her hair just turn black enough. (Using in focus areas works better IMO.)
To get say a proper white to go with your placed black, you adjust contrast, paper grade. That's what the filters do for VC paper.
Changing contrast generally means finding a new print exposure time to place your chosen tone, like that black you are wanting. Use a new test strip to find your black time, then print a proof.
If the proof is still too gray you need to use an even harder paper grade. If the print is too white move to a softer grade. Adjust contrast, find your black time, yet again, and print a new proof and make a new decision, repeat as necessary.
Yes this can be tedious especially when learning, but it does get easier with experience.