I would doubt very highly that the MAP and cruise control would be related at all. I understand the MAP is just before the cables and WAY before the BCM, but those are two diff systems.

iirc, the aft O2 is really not that crucial. it's only used as a comparison to the forward O2. as long as the fwd O2 is reporting good numbers, you should be good. for the degradation of MPG and power...I have no answer for you, sorry.

ummmm...why would the third brake light be a determining factor for cruise? good on ya for checkin them ANYway...but...huh? the loose cable I would address. for no other reason than because it MIGHT jump the groove and cause some bad juju to go down. brake fluid? who ARE these people?

all I can think of for cruise is cabling and the BCM. no, I don't know it all, and I'm not delusional to think that I even know a bunch, so I'm gonna let someone else chime in. but to try to connect the PCM and the BCM like that (MAP and O2 causing cruise issues), I think you're goin down the wrong path on this. good luck, please keep us posted.