Well lets start out by saying you can hunt with both guns as long as you are not using FMJ rounds against the law. Personally I would use the 357 it makes for a great brush gun (light easy to carry) and I think if you put a good scope on it, it will be fine out to 125 yards which is plenty. If you are experiencing drop at 100 yards sight your rifle in at 1 to 2 inches high at 50 yards and then shoot 100 yards. I have taken deer at 125 yards with a 357 lever gun with 140 grain factory loads. As far as ear protection you want to hear the animal so you know what direction he is coming, they do make an ear piece that alows you to hear the smallest noise, but when your gun is fired it cuts off acting as an ear muff. I have never hunted with a mosin so not real familiar with what loads are better than others, if I was using it I would not go over 150 grain, but thats my personal opinion.
Oh and when you harvest your deer take the back strip and cut it into squares and use a meat cleaver, beat it down to tenderize then soak in buttermilk for around 5 hours in the frig, flour and salt and cook it in a fry daddy, you will love it and bring me some.