I do not have a recommendation for you, but I note that Delta Sky Miles are called "Sky Pesos" for a reason. I'll just remind you that as a BAEC Silver you would get free access to AA's Main Cabin Extra (extra-leg-room) seats -- with 35-36" seat pitch on the trans-Atlantic flights -- at time of booking of an Economy Class ticket (including the cheaper Basic Economy fares). No, that would not be the same as a Premium Economy seat, but it might be good enough for you.

For travel to Upstate New York, on Delta you would likely connect at JFK or DTW; on AA it would likely be at PHL or ORD. (And on UA -- if you wanted to consider Star Alliance -- it would likely be at EWR, IAD, or ORD.)