I believe your’ thinking is reasonable about getting
it to run the first time. What do you think about trying this?
Getting one of these and using a socket that fits the
flywheel nut, and spinning the motor with a drill, with the
spark plugs out, to see if it will free up some. You might
also try it with just the spark plug in one cylinder at a time.
The compression might be helpful in getting it to loosen
up some if your drill is powerful enough to spin it.
Tubs.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.