Could you upload your PUP so a brave soul like sk group can try it. It does seem like your PS3 died at a very coincidental moment, if the hybridized FW works, then we maybe able to mix 3.55 with 3.41 and keep the best of both worlds.
Ok, i'll upload a PATCH later... you will run it on your pc, and it will patch your 3.50 PUP
It's actually easy to make one, there is a program posted on ps3news called "gpup" It extracts and packs firmwares (doesn't sign them), it will extract the files from PUP. So i extracted 3.41 and 3.50 Firmware and i opened the "update.tar" that it gave with 7zip.
I dragged and dropped the 3.41 CORE_OS_PACKAGE on the 3.50 "update.tar" using 7zip and i repacked it using gpup, then i flashed it through service mode(Lv2diag.self way)
After that, it blinked green and turned off as normal but then, i turned on the ps3, and i get YLOD and then it blinks red nonstop