A positive and typed swab test for HSV 2 combined with a positive antibody test says you have HSV 2 infection and are potentially infectious to others, even though your outbreaks are on the buttocks.
Yes, you should disclose your herpes status to new partners
Condoms reduce transmission from females to males by 65%
Yes,you can shed virus from the vagina as well. You may end up with vaginal outbreaks at some point, yes.
With a positive antibody test, you are extremely unlikely to get this in a new location, outside of the boxer shorts area.
You acquired this vaginally, but in your case, the virus chooses to travel along a slightly different nerve branch and show up on the buttocks, though it can also be given off from the vagina.
You should consider daily antiviral treatment like Valtrex to reduce the frequency of outbreaks as well as reduce the risk of transmission to a new partner.
Just because your husband has no s/s, doesn’t mean he’s not infected.