Is it likely that this is herpes, and is a western blot necessary?
Given these variable results, I just can’t say for sure and would advise the western blot, yes.
Why would the test result numbers flip like that? Is that showing a concerning trend in antibodies for HSV1?
the tests are unreliable and often give confusing results.
what is the likelihood this is a cross-reaction?
I’m not sure what you mean by this
How would you proceed with this information?
I would get a western blot