IMO moving your flow accelerator wont do much for getting more water to drain into your overflow. The pump determines how much is pumped in which is equal to how much is drained out. The flow accelerator just creates a small amount of back pressure on the return flow which causes it to shoot out at a slightly higher velocity.
What size is your tank if I may ask, and what size pump are you using?
Honestly, I think the valve is your best bet. Pretty much everybody who has a sump set up with the fuge and skimmer lines split have to rely on valves to get the control that they're after.