Michael, a couple of things I can guess at, but first you don't have a true Samson post which is a 4x4 through the deck
and rabbeted into the keelson or stem for strength. What you have is a bitt or more preferably a bollard since it is round and just mounted on deck
. With the same number of bolts in it as in the windlass, the shear load in the bolts will be the same in both, but because of the shorter fore and aft distance of the bolt holes on your bollard, it would have a higher tension load on the aft bolts, than on the aft bolts of the windlass. You would also have a greater compression
load under the fwd edge of the bollard, so if you thought that the snubbing off your windlass contributed to your rot
problem under the fwd stbd hole, then it would probably be worse from the bollard.
You should snub your chain from something as you have no tabernacle, pawl, or cam on your windlass to secure your chain from slipping, and the brake is intended to take the weight of the anchor and chain only, not the force of the boat at anchor. I would suggest mounting your windlass on an oversize stainless plate, with an additional hole it it off to the side, to shackle a chain stopper into. Then with a chain from that to a chain hook, or some other chain grabbing device. That would keep the load low with no overturning loads on either the windlass or the bollard. With that done you can position the bollard so that it lines up best with your chocks for dock
lines, and position the windlass for the best drop of the chain into the chain locker.
Now as to why the windlass was off to port a little I think it was to allow the chain to drop cleanly into the locker through the hole in both the sprit and the disengaging finger (not the correct term) casting (which is not in evidence on your sprit). This little chain stripper would normally be bolted down over (or on) the hole, and has a finger that comes up between the jaws of the wildcat to disengage the chain links when they are under load while weighing/retrieving anchor. The chain then drops through the hole which is part of the same fitting. If your windlass was centered the drop area in the sprit would be a notch in the edge of the sprit which would be structurally unsound for the sprit and awkward for the chain-stripper. Perhaps the sprit should have been a tad wider in that area.
Oh well, thats my thoughts on the issue.