I am running on the assumption that this is kickboxing rules, if it is Muay Thai all that I have to say will still apply but you could knee the body more liberally. He fights too stiff and you fight too loose. First thing is make sure you tighten up your punching technique - because I could those looping punches of yours getting you into trouble.
You need to do three things to succeed here:
1) Counter his kicks with punches and front kicks, he isn't particularly balanced when he kicks and his legs seem overly straight and stiff. This compromises his over all kick and it gives you a good advantage when it comes to countering. His head stays on-line when he kicks dead centre putting his body at an uncomfortable angle. That also means that all you really need to do is shoot straight down the middle. He is making himself quite an easy target. That means you can damage or knock him over without too much trouble if you time your counters well. Make sure that your punches and front kicks hit the body at least 50% of the time.
2) Use pivots and lateral movement to circle out and otherwise avoid his forward momentum. Your opponent always comes in on straight lines. This will mean he runs past you and put you in his blind spot so you can attack. If he commits to southpaw you'll need to pivot outside his lead foot in order to effectively get into his blind spot.
3) You NEED to make sure you're comfortable holding. The rate that he comes forward, if your footwork isn't disciplined enough to get out of the way he WILL get to you and start flurrying, either against the ropes or in the middle of the ring. The good thing for you is that in these flurries he actually overcrowds his opponent. He doesn't keep a good enough distance to pressure with punches but still be effective at moving and trapping, he gets SO close that all you really need to do is tie up.
So my gameplan for you would be:
- Lots of straight right hands and front kicks (specifically target the body as much as you can)
- Pivots off of your left foot, outside into his blind spot
- Deal with his aggression via frequent clinching
The frequent clinching, pivoting and bodywork will tire him out, he has a fast work rate anyway, you keep making him swing and miss, making him fight OUT of your clinch, and keep hitting the body and he will fatigue fast, once he's fatigued he should become more of an open target.
I can see two scenarios that will absolutely play out in this fight:
Scenario 1: He chases you with punches
Scenario 2: You try to avoid his chase but you can't because he hits you with a round kick, blocking your exit.
So long as you understand that the time to tie up and make him fight out of it is scenario 2 - you will be far safer, make sure specifically to wrangle up his arms, not his head.
I cannot garuantee success, but this is the gameplan I would personally use.
Be sure to watch Floyd Mayweather vs Manny Pacquaio and Jerome Le Banner vs Ernesto Hoost (2002 GP) for an example of each gameplan.