I agree with
@Jesus Freak on everything he said.
I have a 62 d6b and I unfortunately do not have a winch so I am unsure of how it operates. I will say that since that tractor is a straight drive that when the main clutch is disengaged that nothing behind the flywheel should have power.
Also with that said the main clutch is a wet clutch so until the engine has been running for a few minutes to warm the oil up, the clutch doesn't like to fully disengage.
I believe that the hole in the floor is most likely the trans fill, mine is fairly close to that area. The 6b is between the steering clutch levers.
On the fuel situation, everything looks good all the way up to the rack movement. The throttle lever should move the rack through its entire cycle. With the throttle fully open the rack should fully open, after the engine starts the governor will pull the rack to governed speed.
I haven't actually had one of those pumps apart but from what I have seen from my parts book and repair manual is that there is a pin of some sort on the rack that rotates a sleeve on each plunger to meter the fuel allowed into the plunger.
My best bet is that the sleeves are stuck not allowing the rack to move.
My setup is a little different than that but the general operation appears to be the same. If you need them I can snap some pictures of my parts book to give you an idea of what you're working with.
James