As you can see he switched to 3-3W-1-2N-1 ; just before the match, to try to play it through the middle since I didn't have any DMC. I had to switch to 4-1-3N-2 (your suggestion Cracicot). And it worked perfect (55/60% possession, I even got a goal) until he switched to his initial 3-3W-0-2W-2, again: )
I then had to go back to a 3-2W-2N-1-2, and managed to get a second goal. He close the gap to 2:1, when he switch to 3-3W-0-3W-1.
Had to switch yet again, to the 4-1-3N-2... things then got balanced till the end. Thanks again for your suggestions. It proved effective especially because of this :