For your filter, you want to clean it when the pressure rises 25% over clean pressure. That means if your clean pressure is 16, you should clean it when the pressure reads 20.
I don't have a DE filter, but you should be recharging a % of the DE each time you clean, and all the DE for the full clean (where you take the grids out and clean them). I'm not confident an the exact % of DE to recharge after backwashing but I think it's like 80%? I believe there is an article in pool school that explains it.