Squats.......... The King of all compound lifts !!!
Though your goal is high for now, it's absolutely possible to obtain. Here is one of the best ways to up your squats.
Smolov Program – Smolov Jr
You didn't list what else your doing but you should also be doing the other compound lifts. You need balance to keep healthy...... you wouldn't only train squats is what I'm saying.
Squat down to parallel or below !!!!!