This Hayward Power-Flo pump should perform well for you:
Hayward SP15922S Power-Flo Matrix 2-Speed
What I can't tell, is whether the pump comes with a 2-speed toggle, or whether you have to add that to the wiring. You may have to call Hayward for that information:
(908) 355-7995 (U.S.)
Mon-Fri, 8 AM – 5 PM
This time of year, plan to be on hold for awhile when you call.

You may also need to put some sort of valve on the backwash line, to avoid blowing sand out -- just check during your 2nd backwash to see if you are losing sand. (You'll lose some fine particles during your 1st backwash, regardless.) Also, the pump may be a bit oversized on high speed, so run only on low, unless you need to run on high.