HSV-2 exposure — trying to understand the timeline and my risk

I’m looking for some outside perspective because I’m pretty anxious about this situation.
A sexual partner recently told me that he tested positive for HSV-2. He said he noticed a blister recently and then got tested. We had vaginal sex and oral sex on August 21. I didn’t notice any sores or blisters on him when we were together, and I haven’t developed any obvious symptoms since.
He told me that his other partners have said they’re clean, so he also doesn’t know where he got it.
I’m trying to understand:
• Is it possible for someone to have HSV-2 for a long time without knowing and then suddenly have their first noticeable outbreak?
• Does the fact that he noticed a blister weeks after we had sex tell us anything about when he acquired HSV-2?
• Does having no symptoms after the encounter mean anything about whether I was infected?
• How soon after exposure can an HSV-2 blood test reliably detect an infection?
• If I test negative now, when should I retest?
• Is there any realistic way to determine whether he transmitted it to me, or whether he already had it before we were together?
I know there’s no way to determine the source with certainty without previous testing. I’m mainly trying to understand the timeline and what my next steps should be.
Please be kind—I’m already pretty anxious about this.