My advice runs counter to what a lot of teen magazines advise, and thus also what people who get their wisdom from teen magazines tend to advise.
Your former friend has already apparently figured out that you're no longer happy with him. He's trying to figure out how to make you like him again. But there is some ambiguity to what he thinks your emotional state is regarding him. The big problem for him is his attempts to find out how to understand you well enough to restore your friendship have precluded him from succeeding in that goal.
Be direct. This probably doesn't feel like it's kind at all. You're telling somebody that you don't like them, which can be emotionally traumatic, especially given that he apparently really likes you.
This is akin to ripping a bandaid off. It will hurt more in the moment, but less in the long term. There's no question about how you feel if you tell him how you feel.
It's not a sure-fire solution. Different people will respond differently to it. Some could decide to get physical, so it's probably a good idea to do this somewhere you have physical back up, or can easily get help. That said, I'd rather suggest you try to not particularly embarrass him in front of everybody else, as that is more likely to provoke an upset reaction - just not necessarily right now while you are in a secure place.
That said, it's my impression that most guys aren't going to harm you if they don't perceive you as having harmed them. If you embarrass them, more retribution prone guys would be likely to want revenge. But if you just tell them that you don't like him and don't want him touching you, and you don't treat that lightly, that's less likely something that he'll feel a need to get revenge over.
I'm a friendly guy. I've been positions similar to your former friend's position on a number of occasions. I didn't ask anyone out through a proxy to the best of my recollection, but I have had "friends" who talked to female classmates as if I'd asked them to do so. For all those classmates knew, I'd asked them out through a proxy. I haven't actually been creeping around to try to find out some way to get back in their good graces, but I have been creeping around them to try to avoid them because I had figured out they were upset with me.
A couple of those women had expressed interest in some light, platonic massage. This was always fully dressed, either standing or sitting, rather than lying down, and always in public. Not being in the loop regarding the rejection they'd sent but I hadn't received, I continued to offer this if they looked like they were having back pain or hand pain (the two sorts of massage the two had asked for previously.) After they'd rejected me to my "friend", they started to tense up if I asked them about that sort of thing, but still responded, "sure" to my "would you like" question.
In those two circumstances, I found out what was up when I finally heard about the "friend" conveying the interest in them I didn't actually have. I didn't ever hear about it from the woman in question.
I also have some experience of listening to what guys say about the gals they're interested in, and the gals they're having difficulties with. Some guys get really angry about these sorts of situations, feeling like they're justified in their position.
However, most guys are at least a little confused by it. The techniques that teenagers tend to use to communicate their displeasure generally don't communicate the reason for their displeasure. Worse, some of it is things that people in high school do by accident, so it's not even a guaranteed indication of displeasure. Sometimes it's even just a bad joke.
I've also seen the responses from people being direct in these sorts of situations, and so long as the person isn't actively cruel about it, it usually goes well, and the guy isn't upset by it. On the other hand, a gal directly telling a guy she has no interest and then laughs about it, or laughs even as she's saying she has no interest, will generally make the guy angry. There's other ways I've seen women express a lack of interest in a man in a direct manner that will generally make the man angry, but they're all pretty obvious things.
Back on my own situation, there was a woman I knew in college that I started out on good terms with, but she seemed to lose interest and distance herself. I really liked her, but I understood she was her own person, so I gave her the space she seemed to want. The last time I saw her, she seemed particularly upset with me.
I don't know what happened there. I don't even know whether I should say I've been baffled by it for over 29 years, from when I noticed her starting to distance herself from me, or over 25 years, from when I last saw her, or some amount of time in between those. I don't even know if she really wanted me to not be someone she ever saw again, or if I took one of the most painful actions I've taken on a misunderstanding (to be precise, that action was to avoid all of the places where I ever encountered her until after she graduated. I did this entirely because I felt like she didn't want me around any more).
She was never direct with me, so I don't know. I've spent most of my life not knowing. My biggest concern is that it was a misunderstanding, and she's spent most of her life not knowing.
Direct communication usually avoids more problems than it causes in my experience. Different people are different. I tend to be very different, but there's others out there who are also very different.