First off I'd say this. There is some variance for bows. The listed draw weight can vary up or down by 3# or so and still be within allowable tolerances. Scales can vary by a couple pounds also, although the digital scales are usually more accruate. That being said, if you really think you need that extra 2# you can add a few twists to the cable(s) to raise the weight to the listed 70#. Frankly, I wouldn't worry about it too much.
The speed you are getting is quite acceptable and the KE is more than anything needed for the largest of North American game. For instance, I routinely have had pass throughs on deer sized game with outfits producing as little as 39# of energy. Speed and energy are nice things to know but in reality are just numbers.
What is of greater importance is having a properly spined arrow that is flying true so when it hits flesh all the momentum is straight behind the broadhead to drive it through. And this depends on whether you can place the arrow in the vitals without hitting bone (ribs are acceptable).
Decreasing letoff to around 70% will, according to all my tests, increase the speed by about 4 fps. To do this you'd need to shorten up the draw length using the draw stop which also makes for a very short, maybe non-existant, valley. You can try it and see how it feels to you, but most like the 80% for hunting purposes.
Really, if the bow is quiet and smooth for you then I'd just be happy and shoot it. As I said, don't get all hung up on numbers.
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