Kylisa, it became possible on Jan. 7 to use US miles for AA flights & v.v. due to their merger. So 35K US is exactly enough to get a free ticket SDF--UVF & return on any combination of the 2 airlines (if available at Low mileage price.)
Amex points can be transferred to British Airways Avios. In fact, there is often a bonus for doing so! The Avios can be used for free tickets on AA now or also on US starting March 31, when US leaves the Star Alliance to join OneWorld. Should cost 29--35K miles depending on connecting city.
Also, BA's fee to change an award ticket is only $40 vs. $150 when using US miles, while AA miles tickets cost $150 to change origin or destination but ZERO to fly from & to the same places on a different day.