When I FT squat, I seem to fall foward while standing up from the squat, even if i keep my elbows high. Does this problem come from weak abs and lower back, like in the back squat?
Sometimes. It can also come from tight calves (soleus mostly) or quads, or from weak/tired upper back musculature.
Basically yes, you’re obviously just going to be more vertical. This means more dorsiflexion and knee flexion - don’t be afraid to let the knees go over the toes as long as the weight stays on your heels.
Practice a lot. Honestly, it feels weird to most people, so just getting used to it will help. If flexibility is an issue rather than just paying attention to it, stretch the lats, rhomboids, triceps, and forearm musculature.
Have a good one,