So unfortunately, we don't have transmission stats for hsv1 like we do hsv2.
We do know that the IgG test - the one that was negative for you - misses 30% of infections. It means you have a 70% chance of that being an accurate result. The test you took for a "new infection" - that's an IgM test, probably, and that's a very unreliable test. That shouldn't have been done on you at all.
So let's assume that you don't have it. There is definitely a chance that you'll get it - we just don't know how much of a chance. What medication is he taking?
There is something called asymptomatic viral shedding. All this means is that the virus is active on the skin - the lips, just inside them, the inside of the nose - when there are no symptoms. This means you can get it when he doesn't have symptoms. You can get it from kissing and if he gives you oral sex. We know that, on average, oral hsv1 sheds about 25% of days a year.
Shedding doesn't mean automatic infection, though. People don't shed for an exact 24 hours on a day they are shedding - it might be for a couple of hours, or an extended period. They may not be shedding enough virus to transmit. We don't even know how much virus is needed to transmit.
The thing about hsv1, though, is that so many people have it. 67% of people under 50 have it globally. Your parents, grandparents, aunts and uncles - a good number of them have it.
You are absolutely allowed to not want to get it. If he is talking valtrex (valacyclovir) or acyclovir, it will reduce the chances by about half.
So. What does all this mean? Definitely avoid kissing and oral sex if he has symptoms. That's when it's most contagious. Some people never transmit it. Others do.
I know it's not the definitive info you wanted, but I hope it helped.