Blowing lines: Don't know
Multiport: If it's a top mount it's easy, assuming you have quick connects on the plumbing. If not it's tougher and you should install them. After that, you just loosen the mounting clamp and lift up. Be sure to dry and lube the o-ring with teflon lube for rubber, then I store it in a zip-lock bag. Side mounts should just pop off with quick connects.
Antifreeze: Not sure but the kind for RV plumbing that's not poison is what you use.
Polyquat: You don't NEED to use it. I like to.

Carl