Looks pretty perfect. I just have two thoughts:
1. The way you have your baffling sketched defies the laws of gravity. I assume that you just drew it that way so that you could fit your text over it, but if not, realize that with your 3rd baffle that high, that's where your water level in your sump will be.
2. Don't forget to account for an air break in your returns. With them mounted that low, if your pump ever fails and you don't have a break, you will have a big flood.
I'm excited to see this one come together!