It sounds like going to this wedding equals nothing but stress and aggravation for you. It is difficult both financially and professionally. I would hate to think that any of our wedding guests had to sacrifice or feel uncomfortable and be stressed about attending a party that I was hosting.
I would discuss your difficulties with the bride. I don't really agree with the "Those who want to attend will," philosophy. Having a wedding on a weekday at an out of town location means accepting that many guests will not be able to attend.
If I had a friend who told me she wouldn't be able to attend my out-of-town, inconveniently scheduled wedding, but would do everything in her power to celebrate before, I'd be thrilled.
In my opinion, making guests sacrifice to attend your wedding is selfish. Making invitees feel bad because they decide that attending a wedding is too disruptive to their lives is selfish. Regardless of what the bridal industry tries to feed us, it isn't all about you just because you're getting married.
I see no reason to martyr yourself on the altar of wedding ettiquette. There is no ettiquette rule that says you must attend every event to which you are invited. Continue being a friend, explain how difficult it is to get away, give a generous gift and get on with your life.