Looks like a decent order. Why do you feel you'll need a chiller if you're going LED?
Check out glass holes..... They sell kits.
Yes, you can remove the top center baffle as the vertical ones within the sump will give you much better support.
I did on my 275 gallon sump and no problems
Of course, if this is for sump use.
This is a simple sketchup I did from your info, if this is how you plan to do it, you don't have nothing to worry about, just look at how much support you're getting from all those vertical baffles.