How should the punctuation work for "and, therefore,"?
It’s difficult to say for certain without seeing an actual sentence. However, a comma is frequently used before and when it joins two clauses, (see?) and, since therefore is a weak interruption it, too, (like too, see?) may be set off by a pair of commas. That background suggests that the first solution might be the most appropriate one.
Since the "Therefore" introduces a sentence that stands on its own, I would suggest none of the above, but rather:
All men are mortal. Socrates is a man. Therefore, Socrates is mortal.
Here is an example of this syllogism.