problem with sump set up

[mountaindew]

I have a 120gal tank with a sump tank.When I bought this 4yrs ago it just didnt seem that it was set up correctly.I am hoping to get help on how this should be set up.The tank is contained with the overflow and diffusers inside the tank.In the sump I have a protein skimmer with 2 small pumps going to each diffuser.Thats were I think its screwed up.As the pics I have 2 pre drilled holes on the side of the sump tank.Im thinking there should be some kind of bigger pump there or some kind of plumbing.I added pics to try to explain my situation.Any suggestions would be helpful

 

[MaiTank]

Is there a problem with water quality? There isn't any need to use the bulkheads if you do not want to. Maybe replace the bioballs with LR if it styas submerged, but basically if the Quality of the water is good and you are not changing any other variables, I would leave it.