Hi Rob, I set my own mooring in deep mud. I used a chinese made mushroom, but Acco chain and Crosby shackles. The eye on the anchor is so beefy that it is unlikely a boat of your tonnage(or larger, IMHO) and windage is going to break it. The lines will go much sooner, as will corroded chain that is mostly in the first few feet under water. Is it in a protected area?
On my mooring, the chain, shackles, everything in the mud looks like the day I installed it.....except it is muddy. I cut out 5 feet of chain before storm season this year, so that's a three year overhaul. I'm in very shallow water, around 5 feet.
I also replaced the buoy with a tube through center style, where the shackle sits on top. This is far superior to the kind that you attach the pennant underwater. My 7 ton boat just went through the worst of Irene on this mooring, it is a much lighter mushroom than yours, but in a well protected creek, and the anchor is buried deep, with the attaching shackle below the mud.
Good luck, and enjoy the freedom and ventilation on your mooring. I absolutely love mine, I'm so glad not to have to be in a marina.