- the wifi antenna sits in the display and the cable has to through the hinge which might cause problems - the rest of your problems sound like an overheating issue or a failing PCB/broken solder point
Would I would d is open the PB and:
- remove the PRAM battery if still there, the main battery will do the same job and nothing serious gets lost when that goes down. Having a slight undervolt in the PRAM battery on the other hand can lead to corrupted data - check the cables in the hinge and see if moving them just a little bit makes a difference - clean the fan and apply new thermal paste (if you want to go down that deep).
Another question is, what kind of HD are you running? I have had 2 cases were the old original ones were on the brink of dying causing all kind of havoc on the MorphOS side while seeming o.k. in OSX.