Hey it seems like we are the same boat. I also preordered the FOTK armor from Anovos with zero building experience. I cant answer much for you but I can answer some, so here are my answers.
1) I cant tell you much. I'm the same height but I have another 20 lbs of beer and love all around my body. Hopefully it fits.
2) I hear alot of people dont like the Anovos ones. I heard they are hard to move in, especially in the joints, and are just straight up heaters when worn. Im thinking of getting a set of cloth ones or the latex ones. As for the neck seal, Im gonna preorder the Anovos premier neck seal. I read that its cloth so for now, that will do.
3) I have the IB boots and gloves. I wear size L for northface gloves and the size L fit me a little short in the fingers but they will do. I have oddly long fingers so an XL will be odd. The boots I bought a 11. I wear 10.5 and have wide feet. they fit perfectly.
4) Cant help much. A voice box, fans, upgraded lens, and aerator are in my list of things to buy. I will do all of htem just because I like the tinkering aspect of it.
5) I have the heavy artillery harness in preorder for anovos. The pauldrons, I hear the White is Squad Leader, Black is Sergeant, and Red is Officer. I would assume this is purely personal choice. As for the SE-11 pistol and F-11D rifle, I purchased some 3D printed guns that will eventually come. But by the looks of it, it is going to be a lot of sanding, sanding, and sanding. I have a "Heavy" rifle because I want to do a heavy artillery stormtrooper. You can get a standard for a regular stormtrooper.