Great advice, Tin! I had to split my tractor to deal with a leaking flywheel housing gasket. Those bolts sere loose enough that I could remove half of them with my fingers! The rest weren't much tighter. Glad I caught it before it destroyed something. The gaskets are cheap enough. I also replaced the rear main seal while I was there since it was cheap enough, too.
Definitely remove, clean and re-torque all those bolts while you have it split. Pull the flywheel, remove the flywheel cover and then put it all back together with new gaskets, Loctite and proper torque. Note that this is based on my 304 Jinma; your 224 may be somewhat different. The principles are the same though.
I would not use a stainless steel bolt for the throwout fork to shaft pin. SS is kind of soft compared to regular steel and may be prone to shearing more easily than a regular bolt or double roll pin. Roll pins are hardened steel, if you weren't aware. Unless you can find a bolt made of 400-series stainless steel, it cannot be heat treated to harden it. All the SS bolts I've seen were made from 300-series stainless, non-hardening alloys. I'd use a double roll pin, myself.