Sorry to hear of your problem.
I used to be a Travel Agent in another life so here goes...
Expedia is only operating as an agent for the carriers. Whatever their rules say apply. Expedia has no ability to alter any tariff, period.
I would get verbally raped by customers who screwed up, told us the wrong dates/cities or didn't think that cancel/change penalties applied to them. The agent, be it a real person or an on-line service is only making tickets available for sale, they don't set the rules.
The times that WE made a mistake, we'd eat it and then try like hell to get our rep to let us off the hook. Once in awhile, it worked.
As for the airlines, it can be a real hit-or-miss thing to get them to waive fees. It all depends on who you get a hold of and how you present your case.
Given the fact that customer service with most of them is a joke and they are swimming in red ink they are more likely to stick to the tariff without execption.
That's one nice thing about using a real, live Travel Agent, you have someone else to verify everything before actually purchasing the ticket.
PS, how's your dad doing?