I'm looking for a comfortable load to shoot
Then why did you buy a 45-70?
Just joking, I just bought one myself, and am already questioning my sanity (not for the first time). Mine is a Marlin 1895, which I have already loaded ammo for, albeit for a friend of mine, because I haven't picked mine up yet. Using a 350 grain Hornady semi-jacketed bullet seated over 55.0 grains of 3031, that thing was beating the heck out of us. That is the way my friend likes them. I am going to lighten them up for myself, but I would imagine your Thompson can take everything a Marlin can, and then some.