Others have used it (the mouse pad) with no problems. Like I said I'm running a modded ER right now and I took a thick
filter pad and superglued 1" squares to the bottom and it worked perfectly. I like this idea better than putting a mouse pad in the water

I've also seen people used dabs of silicone to make little feet for the pumps.
Also, throttling the pump you have back with a ball valve won't hurt the pump. No sense of replacing it if you don't have to right now

It's just like adding a little more head. And your not terribly over the 3-5X, so i would just back it off so that your display doesn't overflow. Unless the nise level on that pump is too loud also.
Good Luck!