You definitely made the hole twice as wide as the nursery pot which is good. BUT you said that you planted it one and a half times as deep. I hope that the surface of the soil within the pot stayed at the same level once it was in the ground. I hope it wasn't too deep.
By the way, don't put stones in the bottom of the hole. That doesn't do anything to improve drainage!
In clay soil if you plant a bush like this in a big enough hole, they will be just fine. It is what you put BACK in the hole that's important!! Peat moss, topsoil, and maybe a little builders sane would work in a poor drainage area.