Hey kda,
Yes, the dolphin striker, which goes through the beam and is welded to the mast step, is free to move up and down.
The beam itself inserts into a socket laminated into the hull. I've attached a photo showing how far the socket goes into the boat. It is integral to the bulkhead.
Yeah, I think the stainless plate performs a bunch of functions; wear, centering, and strengthening.
The rope is actually a stainless wire with a turnbuckle. According to the importer, Pilkington built the boat with this to stop the beam from rotating when "under extreme load." That's never happene