Great post fella, wish there were more posts of this quality.
Get yourself some spun poly or spun nylon nets, 4ft with good quality pegs on them. Avoid 4x or 6z nylon, you'll only end up leaving them behind when you get some better nets.
A couple of thick socks over the water bottle will help, get a spare bottle and keep it indoors so you swap em and let one defrost whilst the other is out with the hobs
Dont worry about only working one hob, when you have saved enough for a second collar then let him work. Some places you will need two ferrets, else the bunnies just give a si