If you want to get to mainline quickly, this isn't the place for you. They rarely street hire direct from the wholly owned.
Met a few guys that commute from Mexico, so it's doable. It sounds like you meet 121 captain minimums, so I'd imagine you'll get hired as a direct entry captain. You can't sit in the right seat for a better schedule when your qualified to be a captain.
It takes a few months to hold MIA RSV CA, and you'd be on reserve for 3 years or so.

1. The commuting rule while on reserve is your primary flight has to land before your reserve period starts. Your backup flight can land after, you just need to coordinate with scheduling.
2. if you have 2,500TT and 1,000 part 121 you'll be a direct entry captain (as far as I know, I'm high time so this doesn't apply to me).
3. MIA is the senior base. There is long call, but it's only a couple lines, and will take YEARS to hold it.