Hello and welcome to the forum. Thank you for your question. Your partner will likely be just fine from swallowing toothpaste in his youth. The main issue that is seen is related to the teeth. The excess fluoride can cause white areas of the teeth to form on the enamel. This is called dental fluorosis and is fine white lines on the teeth. Does your partner have this?
The other thing that could happen but would have happened at the time is stomach issues. Swallowing too much fluoride typically results in upset stomach, nausea and vomiting. Again, this would have happened at that time.
Hello-I think if he was going to have any issues, they would have shown up by now. If you are still concerned, then have a chat with a pharmacist, they may be able to give you some insight as well.
Have you asked your partner why he does this. If he is worried about bad breath, then using a good mouth wash is a better option, but again, it needs to be spit out.
If he does it because he likes the taste, there are plenty of good candies made with mint, or better yet, drink mint tea. It will freshen his breath and also has many health benefits. I love it.