Re: Is it normal for the drive shaft to move in an out by half an inch??
It is your thrust bearings that have failed.
These bearings go on each side of the shell bearings on each main journal and stop crank walk. There should only be tops 8/1000" end play in your crankshaft.
If you have a lot of end play, pull your oil pan off and look for pieces of bearing material. It will be soft metal, peutor in colour.
Eventually your pistons will start hitting the cylinder walls and this will cause serious fatal damage. It's time for a rebuild before it gets worse and costs you some serious coin.