Squats – you can do back squats twice a week. I think only doing them once is for variety and different stimulus.
Abs – train the different parts of your abs:
Upper flexion (crunches), Lower flexion (situps), oblique rotation (russian twists), oblique flexion (side crunches), stabilization (bridges), and compression (vacuums). I've been toying with hitting all these parts lately and it has really helped. 2-3 intense sets of 10-15 reps twice a week per part suffices.