What would you do?????

So I’m getting married in a few weeks and I had a conversation with my fiancé a few months ago about finances. He co-signed on a car for his ex girlfriend (who was allegedly a gold digger) and based on the state I live in if she defaults they go after him and with us getting married they could possibly come after me too. I talked about it with him tonight because his ex girlfriend is also his friend’s sister. So he called his friend who is going to find out from his sister tomorrow. I gave him 3 options since we talked about this months ago after he proposed but I guess he didn’t think it was a priority. He said to wait until tomorrow to discuss it further when he finds out exactly how much is left. Here are his options:

1. Prenup

2. Postpone the wedding until he gets off the car loan or it’s paid off.

3. Not get married at all. That way legally I’m not tied to that mess.

Am I being unreasonable? Also note, I have a mortgage, cars and other assets to protect which is why I mentioned prenup. I been thinking about doing that anyway since we’ll be staying at the house I established before he entered the picture.

Which one would you choose?