I'd be pretty sure you'll need a cool tube or air cooled hood with a 600W in a 1x1x2. I'm running a 250W HPS in a tent roughly half the size of yours (1.8m x .8m x .55m) and without the cooltube id be fuuuuuuucked even with my extractor fan which is strong as fuck. It wont have anything directly to do with humidity (although hotter temps will increase the humidity) so it's really just about keeping the temps down.