When I read the specs, I see that 1.5" x 0.095" is legal. Is there any reason why I cannot use this spec for my car?

Yes it's the min and can be used. Personally I have 1.500 X .120 wall tubing. It doesn't weigh that much more for the added safety.

Not that this focus of my question, but .120 is 25% heavier per foot.

1.75" .095 is lighter than the 1.5" .120, and more stiff, but also more $$, and harder to work with. Having used my rollcage, overbuilt suits me just fine!