Sorry, computer wise, I can't answer your question above...
Heck, I just /finally got your pic opened to see your drawing...
Anyway, looks like a good start...and will "work" as is...
But, here is where you start looking at "trade offs" to maximize potential/minimize problems down the road...
If you build it as drawn (starting on the "left")...
You widened the "input chamber" to fit your skimmer pump...you lost a little fuge space but gained in steady water level for the pump...Water will stay at the level of the "second" baffle (the one touching the bottom) Let's say that one is 14" tall...
Water spills over the 2nd baffle into the 'fuge" area where the level will stay at the height of the 3rd baffle...Lets say that ones also 14" tall...
Then the water spills over into the return pump area...
This is where any change in water level due to evaporation will show up...this area is 14" tall X 12" deep (front to back) X 6" wide (built to fit pump)...This will give you 4.36 gallons for the the pump... But it will run "dry" in about 1/3 that...so you end up with "about 2 1/2 gallons of "evap time" to play with between top offs...Following me here...?
If your evaporation rate is low enough...(gets higher with MH lights and fans blowing for cooling) then this design will "work" ... If you run a "High Evap Rate" let me know and there are some "trick modifications" you can do to "minimize time between top offs...