RE: 50 pound bow
Definitely make sure it is shootable before you go hunting with it...not to mention practicing with it. Any reputable archery pro shop should be able to do that for you.
50 lbs is more than adequate for deer but I would stick with a moderate to heavy arrow and a cut on impact head to maximize your penetration potential.
Max. shooting distance is basically determined by the shooter though most folks keep shots at 25 yards and under.