Lets say you lived in a gravitational experimental room

1) No. Your muscles are undeveloped and no longer fit to withstand the greater effect of gravity. If you sat in a chair for 12 hours, you wouldn't be able to stand normally without wobbling your first few steps.
2) No. Undeveloped muscles as explained in #1. If anything, you'd jump higher when you were back in the anti-gravity chamber for obvious reasons.
3) Yes. You'd be a little taller from not having the effects of gravity on your spine. This is already evident from people being slightly taller in the morning than they are when they hit the hay.

I don't think you read his post at all. He's talking about a chamber that increases gravity, not decreases it.