1. The vacuum reservoir on mine is bolted to the driver side inner fender, between the coolant reservoir and shock tower. Most people would say it looks like a coffee can. There is a pic of my engine bay here for reference:
https://forums.amceaglesden.com/index.php?topic=47004.msg362957#msg362957 (shameless plug I know lol) If you flip the pic right side up, it's the little round can in the lower right of course.
2. I'm not sure exactly where. I'm headed to the shop later today, I can see where mine are plumbed in. I can say that I disconnected mine and ended up hooking it back up. Without it, the transfer case would neutral out sometimes after an extended high-RPM blast. Your results may vary, I'm sure I have less vacuum available with my big ol' Holley on top.
3. Yes. See #2, I'll check later where they are routed.
If you're looking for other ideas to get you by, I thought I saw somewhere here where a guy made a manual shift lever like Jeeps have for the t-case. Or ya could just disconnect the vacuum motor and keep it in 4wd all the time. Won't hurt a thing as long as your tires are all the same...