Here's a link that covers BAC water stability pretty well: https://www.peprecon.com/research/bac-water-stability/

From my own experience I've used 90 day old BAC water plenty of times without any issues, so you should be totally fine at that 90-120 day range.

Went through the same rabbit hole myself. COAs are just a sample of a batch and even reputable places can under or overfill, so at minimum you want to see testing across several markers - purity, endotoxins, HPLC, etc. Personally I lean toward US-based manufacturers with registered facilities because they have more to lose legally and are held to higher standards, even if it costs an extra $20-50 per vial. At the end of the day you're making injections into your research subject, so it's worth doing a real risk/reward analysis - and remember you can always send vials out for independent testing.