filter pumps????

Taking into account the head preasure I would go for 500 - 600gph circulating through the tank. Same thing with the jet system. You will want between 100-150gph per jet.

Here's a calculator that can help you figure the size pump that will work best. http://www.reefcentral.com/calc/hlc2.php

First you need to determine the maximum flow rate of your returns... then to be safe I would stay at least 15% lower than their maximum.

You could connect the sump's return pump to also power the UGJ... but personally I would run them on separate pumps. This will increase the overall current in the tank working against dead spots and/or debris from collecting in certain areas (although to a degree this will always happen). Running them separate will also prevent an imperfection in one system from effecting the entire tanks filtration.

I also confess that I use heavy filtration...

This is what my overflow is---- http://elmersaquarium.com/h109oc_rr_tanks.htm ---
It says there that it is a maximum 600gph overflow, Using a rated 2,400 G.P.H. pump at a 5 foot head. I am assuming that i can use a pump up to 600 gph.

If it has just the one overflow you could use something like a mag 7 and be well within bounds of your overflow.

Here are some pump head charts that might come in handy. It has a list of the most commonly used aquarium pumps along with thier head loss charts. Click the "more info" to the right of the pump and you'll be able to determine which pump is best suited to your needs. Without being able to see your return line I would guess your pump will be fighting 4-5 feet of head pressure.
http://www.reefs.org/library/pumps/