The fort knox system of the french (3. Nc3/d2 dxe4 4. Nxe4 Bd7.. intending Bc6) seems like a good surprise weapon for a 4... Nd7 caro-kann player like me.

The pawn structure seems the same. The ideas seem the same, but somehow my results (from blitz online) are very bad!

Can anyone tell me what are the substantive differences?

My own tentative conclusion is that in the fort knox White can play c4, b3 and Bb2 at total ease (he can't normally do that so easily in the caro without giving a concession like allowing me to play c5, or exchange some pieces). And when my Bc6 swaps with something (either a knight on e4 or f3), White gets to put his bishop or queen on a nice aggressive square on e4 or f3. Unlike the caro, I can't seem to break with c5 very easily in the fort knox. In fact, I believe Black is in abit of a zugzwang. White is less committal with his pieces (unlike in the 4...Nd7 Caro) and can play according to Black's response.  

I do not know any theory on the fort knox, can anyone provide some guidance on where and when to swap pieces etc? Or what I should look out for? I see that sometimes Black can play Bb4, when should I do that?

On the White side, I can't seem to get any advantage against the fort knox either. This seems like one of those annoying openings which one hates to play with BOTH colours. What is White's best setup?