I have removed all the bolts on the clutch plate in a frozen engine by using a socket wrench and proper length extensions and a knuckle at the socket. I was able to access all the bolts from either the bottom or access openning on the bell housing.
You should be able to feel all the bolts from the bottom.
Then you should be able to get to the bolts that hold on the flywheel.
As for the cylinders and pistons. I kept adding lubricant (I used 1/2 automatic transmission fluid & 1/2 brake fluid) to the cylinders and shooting the pushrods at the crank and wrist pins with WD 40. Every night I would go out and tap on the pistons. I took a wooden dowel and a big hammer and go around the outside of the pistons. I thought that would keep the center of the pistons from breaking. And would free up the rings.
After you have the clutch plate, flywheel, and bell housing off you can use a long bar (I used a Stanley flat bar) to slowly rock the rear of the crank shaft back and forth. I used the two positioning pins used for mounting the flywheel.
Just keep working on it. Patience and time is what it takes.
Mine freed up. It took weeks.
I hope this helps.
I went out and worked on the engine again and couldn't for the life of me get to the bolts. I can get to the four bolts on the bottom of the flywheel cover fine, but the two on top I can't. I took off the cover you mentioned, and can see the two bolts in there. I tried to stick a shallow 9/16" socket in there, but its too large. I fed a wire down the flywheel and pulled the socket up to the nut, but with an extension i couldn't get the right angle to turn in, nor did my joint fit.
Am I just having terrible luck or did I look over something else?