Hey Aaron, first of all, welcome to the forum!
The starter gear in your illustration should be free to turn in one direction. The alternator rotor is bolted to the crankshaft, and if it won't turn, than you probably do have stuck pistons. Lots of guys have had good results by removing the spark plugs and filling the cylinders with a mixture of acetone and automatic transmission fluid, which acts as a very good penetrating oil.