Your old pump was ok at 10psi, your new pump is a whisperflow? therefore turn down the speed until you get to about 8-10psi on the gauge and enjoy the massive saving in electricity! As to the leak, hopefully it will stop when the pressure is reduced but 28psi is normally within it's operating range.

I don't know your pool plumbing pipe size or setup or how long you run your pump for but you could, I am sure, set the pump to run at 5psi on the gauge, save even more and no notice any difference or possibly an improvement in water quality as slower filtration is better filtration. On my pool the gauge shows 1/2 of 1psi, the pump runs 24 hours and that uses less electricity than the old single speed pump running for 2 hours.