Hi BNG and a big hug to you on this tough day you're having.
I don't think being friends is in and of itself the risk. I think that shifting this intense relationship you've been having over into another category (the friend category) could mean it just slides back into its previous category.
One thing is for sure, time is your friend here.
Time apart, time to think, time to let the fires die down and so on.
As a complete side note, one thing about all of this I found strange was his parents acceptive response. I raised all my sons as JWs and now we have all left the religion except one son.
No JW parent who fancies themselves a good JW (and a good parent) would be cool with you and he having a relationship.
A "good" JW parenting response would be to warn him off the relationship using scriptures like "dont become unevenly yoked with unbelievers" and so on. If that failed and he kept the relationship going with a "worldly" (that would be you) person in spite of their pleading and guilt tripping and calling on elders in the congregation to do the same, then they would grudgingly accept it. All of that would take time.
In my experience, the less hard core JW parents come around because they love their kids, the extreme ones will shun them (there's a spectrum) but NONE of the JW parents I know would just rollover initially with a casual accepting attitude - especially with a 22 year old.
So that is puzzling to me.
Regardless, I feel for you and the pain you are in right now. Take good care of yourself emotionally and congratulations on being wise for your age.