ar1, what you're describing is what's making us crazy in our house!
Our son "passed" a baked milk challenge last summer. However, he often still has mouth and throat symptoms after consuming baked milk. We have pushed ahead, although we've tried to find that perfect balance between enough milk and no symptoms.
About a week ago, he also had a peanut challenge as part of the FAHF-2 trial. His numbers are very low - lower than your son's. However, he's also had a real reaction to peanuts as a toddler, so we know he is (or at least was) allergic in the past.
During the trial, I asked them what they considered a pass. If he had itchy throat, lips, etc., but no other symptoms, would they put him in the trial? They said they would need more objective symptoms, or that the throat/lip discomfort would have to escalate, not just stay the same, to get in the trial.
I then asked whether they would call it a pass if he had just mouth/throat symptoms. The doctor wouldn't give me a full-out answer because she said she's not my child's allergist, but she said they generally don't consider those symptoms to be a clean pass and that our allergist might have us avoid another year.
It is VERY confusing. I know very few people whose kids were actually allergic to something (not just test results) who can all of a sudden just eat their allergen without symptoms. This seems like a gradual process. The problem is knowing when to introduce the allergen. In our case, milk causes anaphylaxis when it's raw, so the issue is very similar to introducing peanut - if we go too far, we could tip him over into a big reaction. (That hasn't happened yet, but there have been some anxious Benedryl and watch moments (and yes, we do this with the blessing of our allergist).
This is not for the faint-hearted. We're all so conditioned for avoidance that I wonder what our community will do if this turns out to be the only path through.
I don't know if any of that helped. Just want you to know you're not alone!
P.S. One thing they did during our trial was a peak flow assessment. They DID see a drop in peak flow at a point that surprised me - when he just had the "lump in the throat" sensations. You might want to establish your son's peak flow and keep an eye on that as another way to tell if you've gone too far with introductions.