I'm not sure what you mean the charge it gives on hosting?

And nope, if there's more traffic, I can always add more servers. I already have a few high traffic websites using this right now, and my servers are fine.

For the last point, I try to make it only use spare CPU power. You can try it out for yourself - start generating and then go watch a video. Your hash rate will go down, but your computer won't lag at all.