I'll mirror what my buddies GreenMan and Jack said.
Instead of going for more weight on squats, go for more reps. Maybe stick with 225 and just keep adding reps when possible. You have a legit excuse to not go overly heavy (for yourself).
If that still hurts your back try front squats. And if that causes issues then you may have to leg press.
Or you can fire up some Bulgarian Split Squats and really torture yourself. (google/youtube it). These are humbling.
Add the deadlift in if it doesn't hurt your back. Its a great lift.
Stick with basic compound movements if possible. Like your original plan.
Without progression, I am nothing.
PAIN IS MY BEST FRIEND.