OK... so it was in fact the first deflector plate in the sump causing the issue... I drilled (4) more 2 3/8" holes for a total of (6) plus the (2) pre-drilled rectangular holes in the plate. Now my water flows perfectly and my Mag 2400 can't keep up so the RIO 1200 MUST be used.
However, since my water level in the wet/dry is only 3" from the top, (which is too close for comfort in overflowing for me), I think i'm going to buy a Mag 1200 to join the Mag 2400 in return water and use the RIO 1200 to pump through the UV
light and directly into the tank as opposed to back into the sump. That should lower the level in the wet/dry to a more comfortable/trusting height.
@Smitty, the actual height of the baffle plate in the sump in conjunction with the top of the wet/dry is actually a 1/2" lower, so when the water level reached the top of the plate, it was in essence reaching the top of the wet/dry too.
Problem solved... Thanks for all the replies and i will post pix of the completed project for those who maybe interested. After all, Aquariums built into a wall are always cool to look at.