Me too. At your specs you should look at a 300 spine. Quit worrying about punching as much speed out of it as possible. Get the right spine first. With your draw length speed is a given.
Couple other things. The MPro cam on a Moab is not designed for speed so don't think you're going to set any speed records with it. Bows with the Cat cam are for speed. The MPro cam is designed for easy drawing and relatively good speed. If you want all out speed then get something with a more aggressive cam.
Arrows do not have knock down power so don't think otherwise. Bows shoot arrows and these kill by slicing through vital organs, causing hemmoraging. They are not capable of knocking an animal down. Even bullets do not knock animals down. They create shock which disables the animals organs and nervous system causing it to collapse.
Consider that many animals are still taken with recurve and long bows of about 50# or so, with complete passthroughs in lots of cases. These have approximately the penetration potential of a 40# compound bow. You are shooting a 70# bow which is way more than I just described so you have plenty of oomph to kill deer with any properly spined arrow you decide to shoot., but the arrow has to be flying true and hit the vitals. This is paramount.