They may be able to take over his "shell" ie his android body, but Tornado himself, at least before the n52, was a living tornado, so they wouldn't really be able to control him.
His body would attack them, yes, but not with wind powers, as they come from Tornado himself.
Depends on the version of Tornado. Some versions had him as needing the suit to keep his "wind form" together. Some versions are perfectly fine and don't even need the suit to get around. So it really depends on what Tornado we're talking about.
Generally, he goes missing if his suit is damaged or destroyed, only to return later on. He's died a lot, so he's used to having to return to the suit when it gets repaired.
He's a very strange character, in the sense that sometimes, he's written as a wind elemental living in and interfacing with an android body. Then sometimes, it's as if he's an android with wind powers. It's supposed to be the former.