Dogwood is a really nice and strong bowwood. You don't need to chase a ring as you would with osage. Actually, it's nearly impossible to even see the rings in this wood. Once it's finely sanded you see some fine rings, but you can't follow a ring. You don't need to follow a ring, so that's no problem. As long as the back of the bow is the intact outer surface of the tree, you don't need a backing or anything. You can just carve a bow like you would with osage...I'm not saying it's identical to osage, but I think the workability and stiffness are pretty comparable to osage. Dogwood isn't harder or easier to finish than osage, but the large amount of small knots that can be present in dogwood might make it more difficult to smoothen the surface.
Has the bow been fully tillered and pulled to the 80 pounds drawweight? If so, lowering the drawweight may not help with lowering the set it has already taken. In fact, once set is there, it's hard to remove. You could heat treat the belly (=temper) while clamping the bow into a few inches of reflex. Furthermore, when the bow is designed and pulled to 80#, it will get pretty inefficient if you just scrape it down to a more manageable drawweight of, say, 50 pounds. You can easily scrape it down ten pounds, but when you want to lower the drawweight dramatically, you basically have to re-design the bow and decrease the width of the limbs as well. How much do you want to lower the drawweight?
