How should I handle an ex friend who feels like he needs to bully me to raise his own self esteem? (We're adults)

I went to college with this guy 10 years ago and I considered him a friend up until this year. Something changed in him, and he constantly needs to put me down and I don't know how to handle it.

We're both 28, for reference.

Last year, he reported me to the college because I was doing students' homework for them for some extra cash. He said that what I was doing was depreciating his Diploma. I guess I get it, but what kind of friend would try to get me in trouble for something as harmless as doing people's homework? He didn't ask me to stop first or talk to me about it first, he just flat out reported me. Some friend.

Edit: I'm not saying what I did was not wrong. If he valued my friendship, he would have talked to me first. And I would have valued our friendship enough to stop.

I ended up dropping out of the program because of stress. He graduated this spring. I congratulated him and genuinely was happy for him. He then sends me this really childish text, bragging about how he graduated and I didn't. Here's a quote from part of the conversation. No joke, this is word for word:

"Hey [my name], just letting you know that I am an engineer now and you aren't. Also I just got hired at [his work] and am making $34 now just to start. There will be a party at [local bar] to celebrate my graduation. You should come. There will be resumes being taken, you should submit yours, because people like me always need assistants. Even though you are not an engineer by any means."

I thought, maybe he's being intentionally arrogant as a joke that I'm supposed to get. But that's not the case, this kind of talk continued for months. And he means it to be hurtful.

I couldn't take it anymore, so I blocked him on everything I could think of.

A little bit of background information, I recently started my own business making custom tools. This quote was a part of what he commented on my Instagram picture of one of my tools yesterday:

"You should stop posting these online, it's really embarrassing because your [tool name] is such a failure. I should redesign all of it for you because I'm actually an engineer at [company name] and have a lot more experience. I could actually do it right, unlike you. I just might help you if you ask me nicely."

Like, what the hell did I do to deserve that? I don't know why I let it even bother me because of how obviously immature he is being.

I didn't respond. I blocked him on Instagram too, but now he's trying to message me on LinkedIn. Blocked him there now too.

I'm still friends with his brother, so it's impossible for me to completely block him out from my life unfortunately.

I almost want to explain to him how narcissistic he is, and how his messages are an obvious cry of mental insecurity. I know that that would just be fueling the fire though, and would solve nothing.

He deserves to be put in his place. I don't know if that's possible though without me becoming just as petty as he is.

How should I handle this? He's bound to see me in the future, so there's no avoiding his bullshit.

Thanks