I won't give advise one way or the other on this given its a prototype shell, but I never use case splitters because they often scratch/nick the interface between the two haves. I wont even buy a Mac if its chewed up like that. I always lay face down and do the slap on the side as I lift technique and let the weight of the CRT/internals anchor the faceplate down as the bucket pops off. The only machines this does not work well on is the Classics, those are some tight cases!
Remember that the 128k has 5 screws! The fifth screw is in the battery compartment. You have tho remove it, if you want to open the 128k! Some cases of 128ks were ruined because the people tried to open the case and forgot the fifth screw.
I got a bit further - I found a trace that had been eaten through, patched it, now the Mac starts off both keyboard and back power button! Unfortunately, still no video or boot though.
That indicates to me the possibility of more traces.. but so far I'm not seeing any that are obviously suspect.
I will note that while I can power up with the keyboard button, I cannot shut it off with that. Only will shut off with the back power button.