I honestly don’t know much as at all about Lyme disease and it’s impact on HSV acquisition. It can take up to four months from time of acquisition to time of antibody positivity so I’m not sure you can say at this point that you did not get herpes from him. That will always be a moving target for the two of you, the timing of tests, that is.
You taking acyclovir every day is not going to make a difference in acquisition, at least that we know about at this time.
It does seem unlikely that she became infected if she had no symptoms during cancer treatment. Sometimes, that is the first time that people find out they have herpes, when they are undergoing chemotherapy.
The longer people have herpes, the fewer recurrences they normally have and the less shedding that happens. If he is having an outbreak once every five years now, that’s pretty darn good!
Please free to ask me more questions as you think of them.