Undefeated HW

Well, you've got tricky this week so that's a good draw. Usually when guys play that long and can't break .500 there's a fundamental misunderstanding about endurance and conditionals. Remember that at heavies you're not really bound to traditional ideas of what a dancer/kp dancer should do-- When the fighters are by and large similar, a whole mess of possibilities are (and should be) open.

I feel confident his build is:
Str: 7 KOP: 0
Spd: 9 Agi: 9
Chn: 9 Con: 13
Build: VH

I wont post what I calculated your build to be, and I was less confident I had you figured accurately.
Based on how I felt you were built, his HGT+SPD is either equal to yours or +1 from his third fight training. I don't know how the backfire mechanic works on (counter) so if a teacher could clarify that would help. All you have to do is match his HGT+SPD and it backfires, but I don't know if training Spd works towards the backfire, or if it is your base speed. But, if you're confident that you can tie or beat him in HGT+SPD you should have an easy fight.

From WeBL Glossary:
Furthermore, counter-punching may backfire. If a fighter counter-punches and his opponent actually has a higher SPD+HGT, then his opponent gets an increase in AGL and the counter-puncher gets a decrease in AGL.

I notice his plans seems to be the same every fight, except the first, which is the ugliest win I've ever seen in WeBL...
He will counter to the body to start, win the round with power punches, then slap to maintain it. His second fight he should have lost, but his opponent had no endurance checks to know he could get a KO.

I would suggest some light body work in round 1, allowing his plan to switch to (outside) slapping, then I'd tear into his body from then on.
Throw in some:
if endurance_percent > 100 - (round - 1) * 3 then #/#/# (?) lines, and mix them with some if mystuns > 0-1-2 lines
then have some :
if opp = 1 and opp = 0 lines
and you should murder him, he is 3-0 from luck only, this isnt a hard fight i think.

As far as what style, I'd use (clinch) even though I think you have less strength. You shouldn't be too worried about score as this should be an easy endurance KO, and the extra rest from clinching will help you gain the endurance advantage faster, as well the +1 agility will help counter his (counter) should it not backfire after all.