CRJ type is not the same as a Challenger type, although they are similar. There are a few old CRJ 200's which have been converted to business jets, that type and experience would apply directly.

I would not commit to a "career" at mesa (as long as JO is at the helm). Perhaps OK to get your time and move on quickly.

You could do majors if you were aggressive about flying and upgrading at the regionals, and willing to work on a degree while doing that. 8-10 years at a decent major would be worth it. I'd do a program which grants an associates degree at the half-way point, competitive minimums might come down to that. They might even come down to no degree in your timeframe.

I'm not sure about the retirement age.

On one hand the precedent is set for age 67 (Japan), and the legacies training pipelines might get overwhelmed by retirements out of their widebody fleets... might come down to an age 67 band-aid or parked widebodies. That would incentivize congress.

In the other column, there is NO discussion or proposals at the FAA, and ALPA now opposes increasing the age limit.