Also want to commend the OP for actually caring about this situation and be another to suggest the AA credit card route. If you can get approved, it's by far the easiest way to earn enough miles for a premium trip.

For the domestic flights, I'm surprised no one has recommended Southwest... They requite a "person of size" to purchase a second seat but as long as the flight is not completely full, they'll refund the cost of the second seat after the flight. Here is the policy: http://www.southwest.com/html/custom...index-pol.html The Q&A talks about the refund procedure.

Since most flights are not 100% full, this could be a great way for you to not even have to worry about having enough room on the TPA-EWR trips.