The sophistication of your question and some of the terminology suggest you might be a health professional, so I'm responding with professional rather than dominantly lay terminology. Let me know if I'm wrong or you otherwise don't follow.
Those sensitivity estimates are about right, although maybe a bit on the high side. HerpeSelect is more sensitive than Western blot; the latter might be closer to 95%. Also, this relates to time since infection, because it takes longer (up to 6 months, sometimes longer) to seroconvert by WB and usually not more than 3-4 months for HerpeSelect. (The difference is even more marked earlier in the course. At about 6 weeks after acquisition, HerpeSelect is ~80% sensitive, vs ~50-60% for WB.)
There is no known difference in serological test performance for symptomatic versus asymptomatically infected persons. This is hard to study, however, because as you suggest, most asymptomatic persons indeed are diagnosed serologically. Since such people generally don't have positive culture to serve as the gold standard, there isn't any clear way to be certain. But the opinion of the testing experts is that there probably is no difference.
The strength of a positive reaction (ELISA optical density ratio 5.5 vs 4.0, for example) is unrelated to symptomatic vs asymptomatic infection. The OD ratio has only a loose relationship, however, to the amount of circulating antibody; it's not like a titer, for example. That is why the test is intended for interpretation dichotomously, i.e. positive vs negative. I would guess, but do not know, that published data on this are available; if you have access to Medline, see what you can find by searching for Rhoda Ashley Morrow as the author. (She committed matrimony a few years ago. Some of her work was published as Ashley, more recently Morrow; and maybe a couple of papers as Ashley-Morrow.) Or contact Focus Technologies. If you are a health professional (or maybe even if not), they might be willing to share available data.
Regards-- HHH, MD .