I have my own sim business and mentor numerous pilots. I specialize getting older pilots get through 121 & 135 training. I have several guys in their late 50’s and one who’s 60 in training now. If you have 1500 hours and a heartbeat you can get hired at any regional. TSA and Go Jet are real bottom feeders. Strongly recommend other Regionals.
Older guys do have a higher washout rate then the younger guys. But if you pre study the right material and have proper coaching on how to get through training, it’s like a marathon. You can do it. Massive impending global pilot shortage coming to low coast carriers and legacies in next five years. You can make good money at LCC’s now (JetBlue - Spirit - Frontier) we over a 100K year two with real retirements like we have at the Legacies.
A year or two at a Regional and you could get to a LCC and in a few more years possibly a legacy. At United we hired many in late 50’s and even one FO I flew with was 61.
I’d go for it, never live with what ifs, best of luck.