Mast height is 64' plus. Forestay length is about 55'.
Re: insulated s/s lifeline, I use it because it's very easy to handle and, possibly, the insulation helps reduce noise during precipitation events. Can't swear to that, but many have found it so. Thus all my vertical dipoles -- on the boat and at home -- use insulated wire.
Size is relatively unimportant, though larger diameters may have a slight edge. Stainless steel doesn't conduct as well as copper, and RF travels almost exclusively on the surface, so the more the merrier. However, everything's a compromise.
Yes, just form the ends into loops. I've written and posted pix extensively on the SSCA website and others on dipole construction and tuning.