Don't play their game, you'll lose
I've learned not to play that game, hackers by nature have more spare time than you and will ultimately win. Even if you get him back, your website will be unavailable to your customers for a solid week afterwards. Remember, you're the one with public facing servers, you have an IP of a random server that he probably used once. He's the one with a bunch of scripts and likely more knowledge than you will get in your quest for revenge. Odds aren't in your favor and the cost to your business is probably too high to risk losing.
It's most likely not his IP
This kind of hacking is incredibly low priority to law enforcement and the IP you have probably belongs to a server 1000 miles away from said hacker. If you are intent on getting his IP, he may have used a proxy whose purpose isn't anonymity, if you track http headers, look for x-forwarded headers in the offending requests, those will more likely have his real IP if they're there. Nobody bothers with chaining proxies for "fun" hacks like this. But again, don't bother, he's hacked you, he won, if you play his game, he will win again. Right now it's not personal to him so the cost of a DDOS attack on you doesn't outweigh the benefit yet.
If you must play the game
I used to setup honeypots for hackers. When one would make it into my intentionally left vulnerable server in my DMZ, I would place some fun files that look important and lead to other fun goodies that aren't so good for a PC's health. Now if I do setup a honeypot, it's just a logging server with a few vulnerable ports so I am alerted of attempts on my network. That way I can watch a little more closely when it's important.
You're looking at this wrong
When a guy cuts you off on the interstate and you rush up to get him back, his response isn't always going to be good for your health. Instead of getting even, think of your experience as a free security audit where the only expense was doing work that you should have done in the first place. Hackers are frustrating, but the first couple of times you have this happens will change your view of security. But overall....Woooooosah