It's very early to tell with any degree of certainty, what the loads will be like in F on that flight.
YES, Alaska will allow you to pay $50 to upgrade to F, even though you are on an AA ticket.
I would say that it is in your favor that you are on such an early flight.
My suggestion is that you arrive to Airport a full 2 hours Early, if you want to buy an upgrade.
If F is available, you will be able to purchase an UG at CHECKIN. Dont wait for the gate.
My estimate for your success is greater than 60%
Have fun.
Junkie-