I have a 91/30, no experience with the m38, m44 or Finns, but here's what I've found:
I don't find the recoil to be excessive on my 91/30. It's not a .22, but no worse than any other full-power centerfire rifle. I put a folded up towel under my shirt if I'm not wearing a jacket, with a jacket on I don't bother.
In GENERAL, rifles made before WW II (mine is a 1938) have smoother chambers and are less likely to cause sticking bolts (I've so far only fired Czech steel cased ammo and have never had the bolt stick). War era rifles were more likely to have rougher chambers due to wartime requirements, so those are more likely to have sticking problems that can't be fixed with a thorough cleaning.
All of the millsurp ammo out there should be treated as corrosive, which means you clean your rifle the day you shoot it. It's not a big deal at all, the salts the ammo deposits are water soluable (which is why they're a problem, they attract moisture). I just spray window cleaner down the barrel from the chamber end, dry with a couple patches, repeat, then clean normally with solvents and leave a light coat of oil on the bore if I won't be shooting within the next couple days. The bolt also gets sprayed with the window cleaner, then cleaned normally.
As others have said, check the rifling and muzzle. You may find a barrel where the rifling doesn't go all the way to the muzzle, that's called a counterbore and it's quite common. The muzzle was apparently dinged and rather than replace it they simply cut the damaged rifling back a bit.
The serial numbers on the bolt and receiver should match, if not have the headspace checked. People have told me they've never seen a headspace issue on a Mosin, but if it's my face next to that bolt I want to know everything is OK. Make sure you check the firing pin protrusion on your bolt, there's a little tool to do this. If it doesn't extend far enough you can get misfires and if too far it can punch the primer (not good).
The safety can be hard to use, you have to pull it against the firing-pin spring. Some get around that by not bothering with it (keeping the chamber empty for instance). If you want use it in a situation where you need the safety (hunting for instance) the best way to do it is grip the safety with the thumb and index finger, put the butt in the crook of your elbow against the bicep, and push down on the barrel with your other hand, basically using the barrel as a lever to pull back the safety, then turn to safe/fire. I sounds more complicated than it is.
Speaking of the safety, it's one of the safest safeties out there. There is no way that rifle will fire with the safety attached without breaking off a BIG chunk of steel, and there is no way you're going to move the safety from safe to fire by accident (short of dropping it from an airplane without a parachute). It both locks the firing pin and disconnects the striker from the trigger.
Check surplusrifles.com for information on how to disassemble/assemble the bolt and rifle.
Remember that the Mosin isn't as "refined" as some other weapons of the era, it was intended to be handed to, and maintained by, the average peasant. Some have said if you squeeze the trigger and it goes bang you've met all expectations of the designer. For all that I love mine.
