holy. thats alot of reading. anytime my 4x4 takes a **** its usually one of the lines. not sure what T-case yours has, my my vac. switch oh the case, the rubber connector was all swollen and wouldnt keep any vacuum. i had to out new rubbers on it. another spot on my truck that was bad once was (V8 truck) the passenger side mani melted the tubes.
hope this helped at all.
1992 Dakota 4x4 5.2L 1989 Cavalier z24 3.5L
1998 Cavfire SE 2.2L 1987 Cavalier z24 2.8L
2004 F-250 6.0L