For me, it's #2 or #3. On #2, are you saying there isn't award availability for BUF-BOS, so you'd pay $100 for a revenue flight on that leg? I ask because one advantage of AA is that you can keep an eye out for a better routing (i.e., BUF-PHL-FCO) to have award availability and change to it without a fee. However, you can't change origin and destination, so if you can only book BOS-MAD-FCO as an award now, that wouldn't be as advantageous. If that's the case, I'd go with #3. Good to use DL miles anyway, as it's tough to get good value from them, and 62.5k for US-Europe in J is good value