Look, a 60-70# bow is not overkill. Most of the archers out there today are shooting between 65-70#. It's not like you are trying to pull 125#.
My advice is shoot every other day. I have a Hoyt Trykon at 72 lbs. I can easily pull it back and shoot 100 shots a day. Well at least I could. I just took it out the other day since November when I got my deer. Getting ready for 3-D shooting season. I shot 10 shots and was done. I actually struggled a little bit the first couple of pulls. the best thing to do is shoot every other day, and you will get those muscles built. If need be, crank down the poundage until you can easily pull it, then crank it up just a little. Shoot some more, crank it up a little more, shoot some more....etc until you get the poundage you want.
Also don't know if your wife/parents/landlord will like this, but I put a target in my basement at 7 yards. If I can't get to the range, I shoot in the house. Focusing on my draw, my locking point, my release hand, my bow hand. All the little things you need to get down to make a good shot.