I admire your desire for a mid-life career change, but you may be basing your decision on a number of assumptions, some or all of which may not pan out.
With 320 hours, you still have a long way to go before you'll be competitive at a regional, even XJT. Although they've lowered their mins to 600/100 (or so I've heard), that doesn't mean you'll get the job. Most people who interview here aren't offered a position. I don't know anything about this bridge program you mentioned, but again, there are no guarantees you'll get a job here. Regardless, it'll still take some time.
Yes, we're getting another 30 or so airplanes, but any growth beyond that is strictly speculation. Continental is very conservative when it comes to growth and I seriously doubt we'll see any major expansion if/when USAir folds. CAL management has made it clear that they are not interested in being the largest airline out there, and I can't say I blame them. As for the 100 options that XJT has, they're just that: options. Until they're parked on the ramp with your butt strapped in 'em, they don't exist. Also, XJT is dealing with three expired or expiring labor contracts: pilots, mechanics and flight attendants. Until those are settled, nothing is going to happen.
And don't forget that our agreement with CAL expires in 2007. While I think we'll continue to fly under the CAL banner, I also think that the new agreement will include provisions that could affect our growth (ie, letting other contract carriers pick up CAL jet flying).
I'm trying to figure out if you live in CLE or MSP, but don't assume you're going to get a job at Mesaba/Pinnacle or XJT. Even if you do, there is the real possibility that you'll get on at the tail end of the hiring cycle, which means you'll be sitting reserve for a long time. If you live in CLE and happen to get hired at XJT, that may not be too bad; just have a plan in place to dump the kid(s) with less than two hours of notice.
I'm not trying to be doom and gloom, just realistic. At 44, I would bet that you're not doing this for the money. That leaves QOL, which is non-existant if you're at the bottom of the list. Just something to think about, especially if you're a single parent and you may not be in a position to move.