Most of the questions you've asked are things that only you can answer. Is is worth going out of your way for a possible voucher? For me, definitely not. Then again, if it were me, I'd just take an extra day off and make life simple. You clearly have different priorities. Only you can decide what is worth it.

I will say DL is being unusually generous allowing you to change airports for a rather minor schedule change. If they allow you to change airports on your return also (which presumably had no schedule change), then that is extremely generous. I would take it before they change their minds.