Question.

If the water level in my sump is perfect yet I need about another inch in my tank but when I add more water it just fills up the sump, does that mean my return pump isn't strong enough. I have a mag 9.5 with a 90 gallon tank, 30 gallon sump and about 4' vertical with a few 45 turns.

 

Your overflow could also be positioned too low. But I would think your logic is correct

J

 

The water level in the display is controlled by the overflow box and the return pump rate. Adding water will not raise it any higher.
Is the overflow and internal or a hang on back type? If its a hang on then it should be adjustable, if its an internal then its usually fixed and non adjustable but should be set for the optimal height.
How is the return pump plumbed, by that I mean pipe or tubing size, fittings, valves and elbows on both the suction and discharge side. Each one causes a restriction.

Photos of everything would help tremendously. Its much easier when looking at the actual working system.

 

These are the best pics I have

 

Plumbing looks pretty straightforward. I will caution you though, you will probably have noise and vibration problems with the pump plumbed solid like that. Always use a short piece of vinyl tubing off the return pump even if you plan mostly rigid to break up the vibrations and associated noise transmission through the solid piping.

What does the return piping look like once its in the display as far as fittings and sizes?

 

The bulkhead is 1" and the return pipe is also 1" up to the 90 on top of the return that has the siphon hole on the underside blowing air bubbles.

 

Seems like I need to upgrade the pump to the mag 12, I already have a ball valve in place if I need to dial it down.

 

Unless I can figure out how to increase the return flow