I used exactly the same rifle for years. I had 2 "go to" loads: I used 22gr. of fffG and a round ball for grouse and rabbits. Very accurate for head shots out to 25 yds. For bigger critters, I used a 250 gr. pure lead maxi ball and 70 gr. of fffG. It was very accurate out to 100 yds. I also found a huge drop in accuracy if I went over 70 gr. of powder.
BTW, if you want 2 handy-dandy pre-measured powder holders, take a 30-06 case and fill it with powder, then slip a 9mm cartridge over the mouth of the case. You may have to squeeze the 9 shell a bit to get a snug fit, but it's a great measure, in that it will easily slip into the muzzle of the 45. IIRC, it holds about 72 gr. (by volume) of fffG. Likewise, for small game, use a 30 M1 case filled, with a 9 mil over the neck. It's right around 22 gr., IIRC. Either way, you're well below max with either, so if my memory is off a bit, you're still very safe. I used those for years, still do when I take one of my traditional charcoal burners out - which isn't nearly often enough any more.
If you have trouble finding 9 mil casings (yeah,right), I just noticed that a 45-70 shell will slip over an '06 case quite snugly, so that should do.