Him taking Valtrex would not protect him from getting your HSV 2, no. It is likely that the dose he would take daily would be insufficient to prevent latency from happening. I don’t think there is a downside for him to do that but we just have no evidence that that would be useful.
I think soap and water after sex is fine, yes. We aren’t sure how effective that might be, but again, it can’t hurt.
You could also try doing Valtrex 500 twice a day for a bit more protection and to keep blood drug levels more even.