You are putting too much thought into this... there is almost ZERO chance of bricking since you are S-OFF... if you are going to flash a complete RUU-style ZIP like you are mentioning, you should lock your bootloader first (no worries, you are S-OFF, unlocked is not really important it just makes a few things easier).
All you need to do is flash the firmware/radio package you mentioned earlier, update recovery from Amon Ra to something current, wipe and flash ROM. DONE.
---------- Post added at 12:36 PM ---------- Previous post was at 12:24 PM ----------
a. Yes, exactly
b. I like TWRP, many people prefer PhilZ recently, it's personal preference... they all do the same thing.
c. GSM is tricky, the Rezound has very poor GSM radios, even with the current firmware may people can only get 2G/Edge. Personally, I would go back to STOCK (not a stock-ish ROM) by following the full downgrade/upgrade procedure that
@REV3NT3CH has to update to the current firmware and verify GSM operation stock, then flash custom recovery, and custom ROM and test.
It is important to note that GSM is questionable at best on the Rezound without some radio tuning... if you are looking for a GSM handset and planning on using the Rezound, you may be disappointed...
@REV3NT3CH has done some serious work on this, but it is still not perfect. I tried this for a while and gave up and bought a true-GSM handset. With the Moto E at $129 and the Moto G at $179 to $219 depending on variant, it is better to just grab a solid GSM specific phone than to try to get the Rezound to be a GSM daily driver... my 2¢ worth on that topic, I chose the Nexus 4 16GB when it was on sale for $199.
BTW, my son has the Moto G 16GB GPE, he loves it... the battery life is phenomenal, better than my G2, with almost 7.5 hours of screen-on time!!! If my N4 ever fails, I am going for the G myself.