My main point in addressing the pressure issue is that you would be better off energy wise with the 3/4 HP pump as long as you can get it to work properly. If you can move the VRV, you may not need to have the washers in the return in order to use a 3/4 HP. This will also improve the efficiency of the setup.

The VRV can be installed almost anywhere down to a few feet above the pad but on the supply side only. Some installers will put it a few feet above the pad so it is easily accessable for replacement. This works well for two speed pumps on low speed but is not recommended for very hot climates where the water can sit in the panels and heat up enough to soften PVC.