Afternoon folks.

quick question or maybe a series of questions that hopefully someone in the know can answer.

I am flying Alaska Airlines SFO to JFK in 1st with JFK-LHR-DME all on the same PNR. Tickets on BA Stock

Alaska say they no longer have a lounge and no arrangement, however I have the boarding passes for the whole journey.

Question is, can I access American’s lounge?

Also supplementary question, does anyone know the loading on BA174 JFK-LHR and therefore the chances of an AUP as knackered and don’t wanna have an aisle in the dorm

As usual thanks in advance to those that divulge the needed info