As a very rough guideline, I try to keep my first set around 2/3 of the top set and spread them out evenly. That's what you've done with bench and PCs, but you started squats a lot higher. I'd probably have done 60, 70, 80, 85, 92.5 on squats, then make my way to 60, 70, 80, 90, 100, then probably increase all the lower sets by 5 one week. It doesn't make much odds, so long as you've got gas in the tank left for the top set.