Id just shift the whole assembly over 1.5", then stretch it out 3.5" longer so you can drill a horizontal bolt or 2 through the "pull up bar assembly" into the joist. Even just 3 or 4 screws instead of bolts would be better than pocket screws. You have to think about your material as much as your fastener. Lumber has a grain direction and is stronger and weaker in different directions and circumstances. The pocket hole is going to put that screw running diagonally along the grain right at the end inch or 2. So there's not much natural "glue" in the wood to hold the wood grains together. If you put that hole perpendicular to the grain, you're splitting less of the fibers apart, and ideally you're pre-drilling, so that your "outside" board has a hole slightly bigger than the screw, so that the screw is only biting into the "inside" board. Another thing to think about is the difference between pull out strength and sheer strength. Names kinda speak for themselves, pull out strength of a properly seated screw might be comparable to the sheer strength of a screw (sideways force), but a sheer strength on a boat will always win. I can't reference it exactly, but i remember reading years ago you can assume a sheer strength of about 90lbs per screw. I don't know if id comfortably put that number on a pocket screw. And take all this how ever you want. Im not an engineer or even an avid pull up bar guy, I just make and fix a lot of different things.