Bowmalock or also called bowmagrip. It's a crush nut. As long as you have threads protruding it won't come off. I have also machined them to about half their thickness and they still hold.
If there is structure under deck, stringers and bulkheads, 2lb foam. Flotation only. If there is no structure your foam needs to be structural, 4lb foam.
Inside of the tank will NOT tell you the condition of the outside. If it is starting to corrode it will be from the outside and won't be seen from the inside. You would not know until you started getting fuel on the outside of the tank.
Do you have the old one you can get dimensions off of? If so have someone who knows fusion 360 or solidworks draw it up. Then send it to a company to make. There are several out there that will quote you. You just send the file in the correct format.
The layer you have up you probably will have to sand to get a mechanical bond. Corse grit like 32. If you wipe it with acetone and it gets tacky you will also have a partial chemical bond. Also I took small bites at my repair instead of fighting a bigger piece
If you have a second set of hands... get some 10 mil plastic and some gaffers tape. Get the fabric up and rolled out then cover with the plastic and tape it up tight. I did a keel repair that way. I had it taped on one side, did the glass and then folded it up quickly. I was by myself. After it...
Posted before I realized your out of scale..... you should be able to find another ampacity chart for dc though. It will compensate for length/voltage drop
If passenger is to use it while underway it should be rated for such. There is different types. Some are only good for while you are not moving and some are rated for travel.
Mine took a few years to do. Is nothing special BUT I took real care to go above and beyond for the structural integrity so I know what's under the deck. I will never get half of the money I put into in back out if I was to sell and I got my resin below cost and everything else was almost free...
The front of the guard must be above the waterline when moving or it will peel off no mater how well you stick it. Then down past where your boat contacts beach. Plus it cannot be stored sitting on rollers or it will deform
