You are sort of over thinking all this. What you need to find is a bow that fits you - that you can draw comfortably - and that you feel at ease and confident with.
Arrow placement is the key factor in humanely taking down a big game animal, not arrow speed or kinetic energy.
Here in Colorado, where we have the largest Elk populations of any state (over 43,000 Elk were harvested in 2011) the minimum draw weight required for a hand held
bow is 35#.
My wife has been hunting for the past 20 years with bows in the 45-50lb range and almost always gets pass-thru shots.
The Indians that hunted here before us took down Buffalo and Elk with 25# stick bows...
I use a 60# bow for Elk and 50# bows for everything else. However - it would not concern me at all to just use the lighter weight ones on Elk, or Bears, or Moose...
I use 60# just cuz I have them and can.
Find a bow that fits you - practice with it until it is just second nature to put an arrow right where you aim - and you wont have any trouble hunting
whatever your heart desires.
Also - if you are new to archery and it does become a passion - you will be amazed at how much more dw you will be able to gain in a short period of time.
p.s. I am far from being a Mathews fan but the Mission Craze really is a great bow for a young and/or short draw person.