I had some of those issues. (I’m 26)
It took a few months for me to make room for my tongue. Now that I have room I can breath a 10000% better through my nose. Magic.
I just tried spreading my whole tongue on the roof of my mouth and on the soft pallet. Once I figured out the soft pallet thing I saw quicker improvements.
I still have a ways to go though and my tongue touches my molars. It guess it’s fine since I’m making progress.
I would try putting more focus on the back/top of your soft pallet to move your tongue way from your front teeth a bit.
I think a little pain means your teeth are moving so could indicate progress.
I’m not an expert but I hope this helps. Good luck!