Just an update for people to share:
I was finally able to get through the phone line. As painful as the wait time was, it was actually nice talking with the representative.
1) all of us on the original ticket was booked without additional charge. he never even mentioned 25 dollars after I stated the issue from web.
2) not sure about the den membership.
3) the credit would cover the luggage, but way more expensive than online. though I really should have used it because I still can't use the remaining credit on the web booking and it scared me to give them another call.