I have killed deer with a 42# on the fingers bow, but I have a long draw. To get my arrow under my eye - but more importantly to get good alignment I anchor on my upper back molar which gives me a repeatable 30.5" draw. Your draw length does matter when going to very low weight bows (IMHO around 35# is low, above that is not) but not nearly as much as other factors. I think the biggest factor in hunting with any draw weight is to ensure you arrow is flying true; period. I'll take a heavy arrow from a 'light' bow with massive fletching and a heavy front that flies perfect over a corkscrewing arrow from a ultrafast setup 8 days per week.
3d and punching paper can be a smidge different, but for poking holes in things that bleed you want a true flying arrow. The recommendations of using a 2 bladed broadhead is very sound logic.
If you miss any major bones except for ribs, nearly any cut on contact broadhead will do the job; hit something more substantial and you'll certainly want much less resistance thus a 2-blade, preferably long length to width ratio head.
There is almost no end to the debate on what a low weight bow is for hunting, 50lbs is really not a light weight bow. I think it matters more about how far your average shot is likely to be more than the size of a deer in your area (animals other than whitetail may be different) because deer are pretty easy to poke two holes in -- but you have to hit them to eat them!