Yea I would dial back the return pump,

But yea the water should be over flowing over that last panel so it keeps that level am I looking at it right?

Also maybe Ask the previous owner what he did different than your doing

Dialling back a return pump by 50% is not a good idea. You need a smaller pump or a bigger overflow box.

Ideal flow through the sump for that size tank and sump is about 800-900 gph so you should find a pump close to that range.

It wouldn't need to be dialed back anywhere near 50% though. I use the Fluval SP4 on my 93 gallon. After head height loss and loss due to plumbing , 90 degree elbows etc , he is nowhere near 1800gph anymore. If the overflow can handle 1100gph then he's probably pretty close and just needs to dial the pump back a little bit with a ball valve.