My compound bow only has 55 lbs and is perfectly capable of taking down a deer. In most states, the legal draw for deer is usually 45 lbs. I think your crossbow would be more than capable of killing deer or turkeys. However, I have never taken a turkey with a bow, so maybe someone else can help you with that.

Are you capable of shooting a gun? Maybe a 20 guage would do just fine. Or is there some reason you want to use a bow/crossbow?

I think you should contact your local NWTF chapter. They sometimes help disabled hunters and may be able to help you out with what you need. The best way to learn is to go with a seasoned hunter that knows what they are doing.