What you could do is move the return area to before the macro algae area, then tee off your return to bring water to that spot. Although I'd do that more for a refugium than a straight "lets grow macro" mentality. If you are intent on having a macro box, I'd only have 2 baffles installed, simply to have water flow pushing along the bottom as you might have a better job at getting tumbling action that way, unless you plan on having a sand bed there as well, the purpose of the 3 baffle system is to use as a bubble trap, and the last set is more than enough.
I'm sure it's just your drawing too, but I'm not a fan on your skimmer area, make sure your water level is set to be the usable height of your skimmer (usually between 8-10"), but you don't want too much water otherwise you'll have to build a stand for your skimmer to operate properly, and then you run into the issue of having enough room in your stand to remove the collection cup. Another idea too is to remove the skimmer from there, put the macro algae there (or a single baffle between the sock and the algae) then have the skimmer chamber next since your last set of baffles need to be lowered anyways.
And a humidistat could be useful, but I would worry that it would be on all the time. Something like this would probably be great
http://www.ebay.com/itm/Digital-Hum...883793?hash=item4b0c3d3011:g:HL4AAOSwmLlYAEsJ
I use something like this, but this is hardwired into the wall/power.
https://www.amazon.com/Humidity-Con...4197864&sr=8-5&keywords=humidistat+controller
Also, unless you have an airtight sump you might want to just have the fans blowing outward, as the lower pressure inside will naturally draw in air from any crack/hole/etc you have.