I'll tackle the last item you mentioned. About 4-5 years ago, we had a boom tent made by Lee Sail Covers (online) from material called Weathermax80. It's not cheap, but it has been on our boat daily for at least 4 summers and is holding up well. It is water tight and breatheable.
Essentially, it is like a tarp, with reinforced seams and grommets.
IIRC, the material comes on a roll five feet wide, so depending on the size you want, you end up paying for the drop off material as well. We had them send us the drop off, which was enough for us to make a bimini sock.
Hope this helps.