Sort out the alignment of rope on to furling drum so that it is central even when reefed. I suspect that it is cheaper to replace the ast block if it is the type that clamps to the pulpit. On my boat the furler turning blocks were roller race type to remove friction.
You’ll lose the dinghy that way. Floating line is available from Marlow made of Dyneema that will last more than a couple of years in the sun. As others have said, polyprop shouldn’t be near a boat and probably shouldn’t be near anything else either other than maybe cable pulls in dark conduits.
I used to work on a fish farm and we used nothing except polyprop. Awful stuff. It sheds micro plastics due to the UV damage. But it's cheap, easy to splice, and in larger sizes it's pretty strong. The thin stuff loses all strength because the outer layer crumbles in the sunlight.
And there are different grades. Split film is cheap and nasty and has no place on a boat. Seasteel is good though. I used a single seasteel strop to moor my boat for many years.
Sounds like you have a disgruntled neighbour with a knife in your marina.
6mm Marlow has over a tonne breaking load. There has to be something in your furling set up that is causing the line to weaken and snap.
Crikey. Worn out in two months. Just out of interest, is the foil section (that sail luff slots into) turning freely? You want as little friction as possible. Ideally it should be easy to rotate fully furled sail around forestay by hand.
