Yeah, 9. f4 was definitely the most testing and critical response, setting up a kind of a mirror Maroczy Bind with a Marco knight hop already made.
One peculiarity is that White has now exposed the king to a7-g1 diagonal attacks, so my DSB now def belongs on c5.
In this light, I feel it necessary to play e6 at some time anyway, and I see no reason not to do it right now - then I can see what White enterprises next.
[Swapping the b1 knight - a potential defender of d5 and/or invader through b5 - off might be also an idea (I'm brainstorming here, bear with me if it's total nonsense), but I'm not a fan of giving my pair of bishes up that early without any compensation (like the semiopen h-file in Bg6 Nxg6 lines), so I won't regret anyway even if it turns out to be the best in the hindsight. Also, I don't wanna play b6 right away because I want this square to be available for my N (so that it covers a4 as well).]
It's somewhat unfortunate that ganstaman is a specialist in the French with both colours, but that disadvantage manifests itself in almost any viable Black opening vs him because hardly any of them can do without the c5 break, imho.
In this position, after 9... e6, White can't really do anything to prevent the c5 break, it seems (except playing c5 himself, in which case b6 looks possible for me after covering c6). White can create a passed IQP by d5 exd5 cxd5, but I think it will be rather a liability for him, though it looks like he's going to keep it OTB for a while as I can't attack it enough times ATM.
One thing to note is that I have the option to insert Nb6 before exd5, in order to prevent Qa4. If then dxe6, then Bxe6 with good chances for Black. But I don't really fear Qa4 as a response to exd5, as I can then play d4 to get a tremendous protected passer.
Another thing to note is that I have to play a6 after his cxd5 in order to prevent Bb5.
10. Be3 seems the most critical response to my 9... e6 - it does prevent the immediate 10... c5 in a way - though I'm covering c5 twice, White can insert 11. Qa4. I can select the calm 10... Be7 instead. But another idea worth consideration, which I like more, is 10... Qa5 11. Bd2 Qb6 12. Be3 c5 - now, after 13. Qa4, d4 does hang, with a tempo.
White can also try 10. g4, but I don't fear it either, because my N will now feel pretty comfortable on e4 if chased away by an immediate g5, otherwise I'll have time to insert h6. And don't forget that this king exposure can backfire on White because I still have O-O-O available.
10. Re1 ideas might be nasty for me. I should delay c5 in this case, as otherwise, after 10. Re1 c5?! 11. d5 exd5??,
White has at least one winning tactic, which I'll leave as an exercise for you and tell the solution in my next post itt (so don't open spoiler(s) there until you attempt to solve this puzzle).