Thanks for the files.
After baking, in your case, from Level 6 to four, you can set the model to four. The fine details are supposed in the textures. I guess I echo here the instructor only.
The UV works but is not without limitations. Typically a seam should be set where we have the least amount of attention.
Go to the Asset Browser and call up the Generic head. Explore how you can paint on it.
I have a short screen capture below, showing pretty much only the forehead of your model. I hope that is OK.
First, I paint directly on it, and you can see where the seam is and that the UV Island has not exactly the same size. Hence the change in the brush size. It is clearly visible.
This can be avoided with the projection painting, and only a little bit shows up.
However, to get a UV that has not a seam in the middle of the face is preferable.
I was able to paint without hitting the border, or was the seam the problem, to begin with.
Please be aware that any change of the UV will change the baked maps, or you work with several UV tags and materials. I would try to avoid that.
60 sec screen capture
All the best