Hi, Here's a couple random thoughts...

If you haven't bought any shade cloth yet, check out alumi-net. It's supposed to be cooler underneath, then regular shade cloth. Seeing as how, your air temps are so high already, every little bit might help.

A 2000 gph pump is pretty big, in my opinion. You could go to 1/2 of that or even slightly less. You would need to drop your size of your stand pipes. Less $ to buy it and less $ to run them..
Have you read anything about 'affnan bell siphon' ? Affnan has designed bell siphons that can start with less water flow ( less electric costs) And they don't have breather tubes that need cleaned.

Danner brand water pumps are pretty good, see the link below, they carry them.

A few web sites you might like...

http://www.aquaticeco.com/
It's fun looking at all their stuff. They have sales pretty often.
They have uniseals, also check out... 'economy bulkheads'. They are only a dollar or 2 more then the uniseals.

Search for US plastics (in Ohio ?), they also have uniseals and bulkheads, and if I remember, they are a little less costly.

http://www.jehmco.com/html/heaters.html
Go to the bottom of this page, you'll see stainless steel tube. It might work for the heat exchanger line in your DIY cooler.
I think I remeber someone here, getting a SS coil at a beer making web site. They used it on their DIY cooler, in the fish water.