x201/x200 fanatic - host of issues, thermal pasting with PTM7950 etc

[xannnnnayz]

First post, been browsing the forum for years. Currently the collection includes:

x201 i5 - OG I picked up in Hong Kong back in 2010. Aside from swapping out the LCD cable, its been with me through thick and thin.
x201 i5 - refurb I got for parts (LCD cable), plus it was dirt cheap.
x201 i7 - *pristine* "for parts" I snagged for $30. Later found out it was BIOS locked, ran fine initially but something happened and now it won't POST. The LED lights blink, fan spins momentarily, but then just stops. If I leave it, I can feel the heatsink getting hotter as time passes.To solve the bricked i7, I just transferred the internals. I know it may have dubious origins, but it does seem relatively unused as after an i5 mobo swap, it runs so cool and I'm pretty sure if I got a new Lenovo 6-cell battery it'd last 8 hours like it did back in 2010.
x200 - $50 for a pretty decent condition, was mostly intereted in the ultranav dock it came with.


The issues:

1. Just to get this out of the way, but from my research, flashing the BIOS of the bricked i7 won't resolve the not-POSTing/not powering on issue, since the power on instructions are on another chip close to the GPU, right?

2. Honeywell PTM7950: anyone have any experience using with the x200/x201? From previous attempts, the CPU region ends up with a very thin layer with most of the excess flowing into the cracks. I also tried to forgo a stock thermal pad for the GPU and use 2 layers of PTM7950, but not sure if this is going to work.

3. Saved the most blasphemous for last: I switched out the x200's mobo for a spare x201's i5. I have very litttle experience with repairs, so I'm not really up for something like corebooting yet. At this stage, I've only used a CH341A to try flashing two bricked i7 boards. First attempt using Windows was a fail, but I think using flashrom worked (still need to test out the board).

tldr: After so many stripped screws, teardowns, failed heatsink refits, I'm honestly at a loss as to what to do at this stage. Ideally it would be great to get some feedback on the thermal pasting, and afterwards I might swap back the x200 to stock for the future coreboot. Thanks for reading this rant, and thanks to this community for helping me out so many times in the past.