Acreagedad - If it is true that your current pump is only supplying a trickle of flow back to the tank, you obviously need to do something to remedy the situation, otherwise you are continuously recycling the same sump water through the skimmer and fuge, with very little water being exchanged with the display. Also, you shouldn't have to worry about undersized overflows if they are currently only handling a trickle. A bigger pump, or switching the skimmer and/or fuge to it's own pump are both possible remedies.
Note that if the "trickle" you are describing is anywhere over 400gph, you have enough tank-to-sump flow as it is. IME, overflow and return rates are typically much higher than is required. Most of the "experts" seem to recommend 3-5x display volume. In my 125g, I'm running a Quiet One 3000 (780gph), that supplies some flow to a remote DSB as well. I estimate 500gph actual return rate (I have very little head, as my pump is actually above the bottom of the tank). For more in-display flow, a closed loop or powerheads are recommended. One way to test the flow rate would be to empty the display a couple of inches below the overflow. Make a mark with tape or something about .5" above that waterline (to give the pump time to get going to full capacity and clear any air from the lines). Put another mark exactly 1" above the other. Turn the pump on, wait until the water reaches the first mark, and then start timing. When the water reaches the second mark, you have filled the tank with approximately 5.5 gallons. Divide the time needed into an hour, and multipy the resulting number by 5.5 to get gph (if it takes 1 minute, divide into an hour = 60, 60*5.5=330gph).
I think if you posted a picture or schematic of your setup, it would be easier to offer specific solutions.