You are comparing apples to oranges by comparing draw weight (lbs.)to Ke (ft.lbs).
What you do is make a draw force curve, record the draw wt. for every inch of draw, from brace (0 lbs) to full draw (center of the valley). Then you total the area under the curve ( potential energy or PE). This will be in inch lbs., so divide it by 12 for ft.lbs. Then you divide KE/PE and you'll have efficiency (%). Generally, you will have less KE than PE because nothing is 100% efficient due to losses to hesterisis (friction in the wheel bushings, resistance of arrow being pushed etc.).

Personally, I like to shoot fixed broadheads with fixed pins @ 275 fps. Broadheads fly very good at this speed and there is a suitable gap between the sight pins (not too crowded). To get the KE I'm looking for, I change the arrow weight and the draw weight. For me @ 64 lbs draw wt. with a 425 gr arrow I get 71 ft.lbs of KE. At 80 lbs draw wt. with a 525 gr arrow I get 88ft.lbs of KE.

Heavier arrows have more momentum, are harder to stop (more penetration). Bowling ball @ 2mph into a window or a ping pong ball @ 200mph into a window. Also, a stiffer arrow will penetrate better than a softer one because it will not scrub off as much energy while passing through an object. All arrows flex while traveling, when they contact the target, the stiff ones don't flex as much as the softer ones, therefore they penetrate better. This is hard to explain, but if you watch the slow motion videos of arrow flight, you'll see what I mean. I hope this helps.