I haven't looked thru your calcs carefully. A couple of things you may want to consider:

A friend of mine buys the cheapest line he can find and rigs up on the beach to determine the line length he needs, then goes and buys the right line.

You might want to consider that an ARC22/Supercat22 is about the same dimensions you have and could check your calcs based on what they use.

I would start with about what you calculated, add the idler block that Jake suggests, and see how it fits. If it too short, it is not as big a deal as it used to be with low-tech line, and a little effort. Hi-tech line can actually be made longer by cutting the core and pulling it out the ends. For the N6.0 I bought 60’ for the halyard, cut the core (Not necessarily in the middle), pulled the core out both ends, effectively creating a taper and about 83’ of halyard.

With the size of the spin you will be running, you will want the ability to double the active sheet, creating a 2:1 purchase. It is very easy and not that expensive to setup. This 2:1 part of the line and any part that is in blocks during active sheeting could be just core or tapered line.