Welcome to the STD forum. I'll try to help.
It is highly likely you have HSV-2. At an HSV-2 ELISA index of 2.56, plus a negative result for HSV-1 (under 0.91), probably there is a 90% chance the test result is accurate. It's not quite certain, and perhaps you would like to consider a confirmatory test. If so, ask your provider about doing an HSV Western blot test, the ultimate gold standard for HSV blood tests.
In addition, as the sex partner of someone with genital HSV-2, probably you have been repeatedly exposed to the virus over the years. You might have been the source of your wife's infection, but not necessarily. If you can provide a bit more detail about her diagnosis -- the severity of her symptoms, exactly what tests she had that showed HSV-2 -- we might be able to sort out whether her current problem is a brand new infection or a recurrent oubreak of something she has had for a long time. But this really may not matter much. Either way, this situation doesn't necessarily imply that either of you has had other sex partners during your marriage. Apparently new genital herpes often pops up in permanently monogamous couples.
If you are infected, the height of the ELISA index makes no difference. In other words, it says nothing about whether or not your infection is new or old, or how "active" the infection is at this point in time.
Here are two past threads on this forum that discuss HSV-2 blood test results and also issues of herpes in couples. You can use the search link to find numerous other discussions. Please take a look, then feel free to return with any remaining questions.
http://www.medhelp.org/posts/show/1129740
http://www.medhelp.org/posts/show/593272
Best wishes-- HHH, MD