First 40 is definitely not too late, while you’re not young. you’re certainly not old either. The bigger issue is your criminal record. I’m not going to lie, that’s a problem. There’s actually a provision in the FARs regarding earning your ATP license that states “the candidate must be of good moral character” which the FAA could potentially question as you’re asked about and convictions on your medical application. Second the airlines really don’t like felonies. Airline pilot can be somewhat of a “high profile” job as you’re publicly representing the company. If there were an incident and your background came out it would not look good for the airline. What I would recommend is you contact an AME (Aviation Medical Examiner) and ask about obtaining a First Class Medical, if you could that would take care of the FAA aspect. As for employment I would contact some Regional airlines and ask them directly. Know that your chances are getting to a Major are not good.