Herman,
I have read this whole thing (man am I tired) and I consciously decided to go with a reduced overflow/return water turnover and use the internal flow of the tank via a mag7 plumber with a spray bar to dispure the flow.
If you notice, on center of the overflow, there is one cut in one of the teeth, that is where I hung the mag 7. I also cut down the return flow cause I was using a mag9 and the drain couldn't keep up - that, of course didn't take into consideration a durso.
I would try and do a durso for the drainpipe - I think a 1" line has a flow through of 1200gph? Deanos, linkman, help me out here
I would get a TUNZE 6000 on a controller and hang that badboy on the center overflow like I did the mag7 and use a mag9.5 or equivalent flow from the sump to run through the squirt - I would also put a ball valve between the return pump and the bottom of the tank so that if the Durso doesn't keep up, you can dial it down. Not the best use, of course but you can make up the flow rate with the tunze.
Hope that helps, also, you should see my setup in person for ideas on the squirt.
House
I would eliminate the squirt and keep the