When I once accidentally mounted my slave cylinder to the rear, I had a trouble. Are you sure you can't move it to the front, put the forked push rod in the correct lever hole, and get that play down to .1 inches?
That piston can't be fully "out" when you adjust. The return spring, which should be in place, and the process of unscrewing the push rod are to assure that the piston has plenty of travel to move that lever arm on the transmission when the clutch pedal is depressed.
The piston can't already be pushed up to the internal circlip. Also, be sure you installed the piston and internal spring correctly.
I'm not saying the problem isn't a stuck clutch, but I've not had that experience.
You'll be driving soon.