Since your arrival at MIA was delayed by DL for >6h, you probably could ask for:
- credit/voucher comparable with "standard" >4hr mechanical delay ($400+);
- some miles if you can politely explain that you should be in MIA sooner than DL bus;
- some miles for oxygen mask experience.

I would try to focus on the 1st and the last.
I believe, car is a weak point, it's not much faster than bus.

Good luck.