jd45-
I suspect that cabin4 is plugging for the 44 Remington mag for the same reasons that you're a pundit for the 45 Colt. The 44 is a good round, and it's done what he's asked of it. The 45 certainly has a lot more potential, properly loaded, but we're giving advice to a 13 year old shooter that may not have easy access to reloading equipment, and he may have limited funds for factory ammo. If you shoot 5 deer through the ribs with a 44, and 5 deer through the ribs with a well-loaded 45 round, you're going to have 10 very dead deer. For a 13 year old deer hunter, the 44 is probably the way to go.
Let's take this back to the original question. If deerslayer was set on having a 45 lever gun, he would probably be better served by a 45 Colt, rather than a 45-70. Even "mild" 45 ammo will blow right through most deer, broadside, and the recoil will be easier to manage than a 45-70, given similar rifles.
However, he made his choice, and it was a great one. He latched onto a 35 Remington, and he even had enough class to put a peep sight on top of it. It also sounds like he has a 280 to fall back on, so he's already one very well-armed hunter.
Deerslayer, good luck, and let us know if you get to fill any tags with that 35.