The few times I've claimed trip in vain, was right at the beginning of trip, so no trip taken at all. Regarding your questions, here my thoughts,

1) If TIV, technically you shouldn't get credit, but don't be surprised if you do if your FFN was in the reservation.
2) Reimbursed, yes, but only for the ticket cost. Best to do double check with AA, as nowhere in your story detail is there any mention of you communicating TIV to AA or EXP rep
3) Carrier (AA) is not responsible for any expense you suffered due to a weather, only for mechanical situations, if you are a High Valued Customer, you "might" get some love by AA, but that is not always a guarantee. Does OPM card has any insurance for this type of situation?
4) Follow up in case OPM does not see any refund on ticket. Check my comment on #2 .

Me, I would not have risked a connection flight, seeing that if a mainline plane was canceled, there would have been a high chance that regional plane would also have been canceled. Always check your options and make sure they are feasible.