Most of your questions cannot be answered with any degree of accuracy due to the ever changing variables. I will say this; you seem to be taking a business like attitude at considering cost vs reward. That's a good thing. Most jump in without looking. They make the decision on emotion then feel bad when the payoff never arrives.
The next 5 years are going to be rough for several reasons.
- Age 65
- Mergers
- Economy cycle winding down
- Jet fuel
- EPA issues
- ATC issues
- MPL on line before the current 60 year olds turn 65
For the first time in history the airline management teams are speaking with one voice and saying something they have never said before in unison: "Capacity needs to come down".
We will see if they really mean it.
Good luck to you.