Is a hsv igm & igg blood test helpful after g herpes exposure 6+months ago? no genital outbreak, other symptoms, but have had mouth cold sores before.

Probably yes: The HSV IgG tests are excellent, and a negative result for HSV2 6+ months after exposure shows you were not infected. The HSV1 result should have been positive if your diagnosis of past cold sores is correct, but once in a while the test misses HSV1 (but rarely HSV2). The IgM result doesn't help one way or the other -- it's inherently unreliable anyway, never done by herpes or STD experts.