Teddy,
I wouldn't worry too much about the velocity. Most of your baits are going to be around 25 yds or so. That 45/70 with those bullets producing a reasonable velocity will thump any black bear at that range. I have lived in Maine my whole life and have been around a lot of Bear. They just are not the ferocious beast they are sometimes made out to be.
Sorry to hear about the poor experience you had hunting in Maine, bear hunting here can be spotty some years. Depends on how harsh the winter was, how the mast crop come through that fall, and in the fall you just can't get as many bears to bait as you can in the spring. Unfortunately, there is no spring hunting here anymore.
Barry