Yes, you can get herpes even with condoms. Herpes can get be rubbed into the skin by areas that are not protected by the condoms.
Yes, even though condoms lower the odds of transmission, specially in the area that is covered by it.
Blood tests for herpes take up to 3 months to become positive and therefore reliable. So make sure your boyfriend gets another test within 3 months to check with the results stay the same. If he gets other sores in the mean time, make sure they swab it and type it.
Have you been tested yourself?
So is it possible to get it wearing a condom?
Because he most likely already had oral herpes. Just because you don't get outbreaks doesn't mean you don't have it. Most people don't get outbreaks and most have no clue they have this virus. Probably got it as a child as when most people do. As far as the blood test this early on, it's not going to reveal HSV2 if he has it since he needs a few months to build up the antibodies. He may not have herpies either but you have to assume he does so you are aware of this possibility. Bottom line, not sure what he has and a blood test isn't likely to be accurate for a few months. He might have had protected intercourse with her but if he was grinding with her without a condom, he probably caught it then.