Lot's of questions. Others are better to answer than me except for the last one. I have a '80 fuel injected KZ1000 (G1 Classic). I am still running the EFI as are a couple others on the site. Mine is working fine as is one other (The Gringo), but most of the rest of the people on the site have coverted to carbs. Seems there were problems with the systems on this model. I know that its not tunable and can crap out without warning. If you buy it and covert to carbs, there are probably a few people that would line up to buy the parts just to keep as spares.
Not much of an answer, but maybe a little more info.
Good luck, hopefully someone else will fill in some more blanks for you.
Also, welcome to the site.