The swivel is most likely the weakest link in the system. I am considering putting a length of chain in parallel with the swivel to act as a 'fail safe' just like the chain bridle is. Normally neither will take any load.
We don't use mushroom mooring anchor here. Can't say I'd have very much faith at all in a weight that is only a few hundred pounds. Once it has pulled out the boat is essentially free. At least with a substantial weight the boat still has to try & drag that around.
Here in Bermuda mooring weights are well & truly weights. In my storm mooring system the weight is a 1 1/2ton cylinder sleeve from a powerplant engine. Attached to this is about 12' of heavy anchor chain, like you would expect to see used on a large harbour tug or destroyer sized ship. Attacthed to this is the swivel then about 30' of 5/8" riding chain going to the bridles which are about 12' long.
All this totals approx 54' from the weight to the bit on the bow in water that, at normal high tide, is about 10' deep. It takes one helluva pull to straighten out all that chain. It makes a wonderful shock absorber under all but very extreme conditions.
Nothing s absolutley safe. This happened to my workboat which was on the very same mooring that my Albin is going on this weekend in preparation for Florence.
This boat is 6,000# lighter than the Albin but it SNAPPED a 1 1/4" nylon bridle. In this case the best that we can figure is that took a direct hit from a tornado, shot across it's mooring, pulled tight like you would breaking thread with your hands, & snapped the bridle. This happened after surviving at least 8 hours of hurricane force winds.