yeah the rake is heart breaking lol, i feel i can absolutely crush 5nl and can get a decent win rate at 10nl consistently, but do find the level of competition is definately better. I am also play soley on ACR for the time being and their 27% rakeback is pretty good compared to some.
I definitely find 6 tables at once it optimal, with less I get bored and play too loose pre-flop and with more my post flop play suffers.