I have made caramels but it did not reach 145 temp required... Can I reheat to temp or can I make caramel sauce and can it?

If there is dairy in it already, I wouldn't reheat. The high heat your sugar needs to reach in order to thicken would most likely scorch the cream giving it a weird taste.

I don't know about reheating, but caramel is unsafe to can at home - it simply isn't acid enough and products with dairy in them can't be safely canned at home.

You can definitely reheat to the appropriate temperature! I would not recommend canning unless it is a tested canning recipe -- unless you're "canning" it in freezer jars.