Variable speed pumps are a nightmare. Look into a simpler mechanical valve. Cycle Stop Valves Inc. www.cyclestopvalves.com.
The Cycle Stop Valve can work with your variable speed pump and make it work right. I suggest that you go to their web site, find their 800 # and call them. They can walk you through solving your problem. . . simply.
NGWA.org "Master Certified Ground Water Contractor"