You say you’ve tested negative for herpes 1 and 2 antibodies, while your partner has tested positive for the herpes 2 virus, though he has not shown symptoms. I don’t find your situation unusual, and it does pose a bit of a conundrum. The reality is that using condoms is the most reliable way to prevent transmission, but in a long-term relationship, I understand that it’s not desirable.
I find that the most up to date and reliable information regarding HSV (and other STIs) is the Centers for Disease Control and Prevention (CDC), which is what I use to counsel patients:
What that last point means is that ongoing daily treatment with a prescription for an antiviral therapy by the affected partner can be effective protection to reduce the chances of transmission; “episodic therapy,” meaning the antiviral is taken only in cases of an outbreak of lesions, will not provide that protection.
I hope this is clear! You can have intimacy confidently, and I’m glad you’re researching the steps to take!