Range,

I had an original Buckmaster which was shot at 29" of draw at 70# with a 350grain arrow. It shot right at 290fps and the KE was about 65#. However without knowing your brothers arrow weight and the speed your only guessing. I guess you could compute the arrow weight then we can have something to go on. A lot of the arrows speed depends on how the bow is setup as you know, ie. the type of rest, how much stuff on the string ect, ect, ect. The range of performance that you mention is very wide, just the difference in 1" of drawlength is about 10fps and 100grains of arrow weight is about 20-25fps. Not so easy, but the differences cam make quite a bit of difference in the KE value.

Aim Hard!