Welcome to LOC.
Congrats on the new car, and must admit a very brave buy with so many known issues.
The mounts should be available from breakers, I've never known anyone need them before, so they shouldn't be that rare from a breaker.
I'm not aware of any sensors in the seats to manage airbags, so if the airbag lamp is on, then I would suspect there is something more drastic going on. The fault codes are pullable as described in the link.
Siezed calipers is a common issue on most older Lexus models. They will come and go, and generally be a bit of a pain unless you overhaul the calipers and slide pins. A company called BigRed do the calipers ata very decent price, I think my two rears including slide pins cost £50 for the pair when I got them (a few years ago mind you).
Any reason for thinking the MAF needs to go?
Aircon will need recharging if it isn't blowing cold, but until it is recharged, you won't know if there are any major leaks (generally it will only need to be redone if it leaked out - unless someone inadvertantly let it out of course which would be unlikely).
The OD light flashing does indicate a fault, not sure of vibrations causing a fault to register, but I guess that is possible if the mounts are that far gone.
Good luck with getting it sorted, I can't see it being a terrifically cheap unfortunately.