After reading your posts, I'd bet any gate agent would be thrilled to work with a pax as savvy as you are. Jethawk's advice (and Mig's!!) sound spot on.
I'd stick w/JFK, too. But that would be based on loads. I don't usually book buddy pass riders until a few days prior. If loads are wide open I will do so a week before.
Keep in mind, you won't have an agent at JFK gates until 90 mins (if that early!) prior to pushback. You can prob find a redcoat tho.
I lvoed your comment about thrills and chills as a nonrev--hopefully, to rephrase, "you're not going to be in for a bumpy ride"