there is not a lot of training you can do in the time you have left that will help. I suggest your training should be easy to recover from. A couple of ~60 mile rides in the first of the 2 weeks should be okay. My issue with multi-day rides has always been getting up and riding on the second day. Once I get 10 miles in, there aren't any problems continuing. So your second 75 mile ride could be a 25 mile ride instead.