1) how low is genital to genital transmission when a possible sore is present?
well, probably significantly higher is having intercourse with a sore present
2) can I get infected by hsv1 orally and genitally at the same time?
Yes, you can.
3) typically how long before hsv1 antibodies are detected on an igg test? I did have some risky sex (we were broken up briefly) 1.5 months ago before my outbreak. My igg was neg when I had swab and blood test done 4 days ago. Would antibodies appear on my test at this point to rule out if it came from my boyfriend or my random hook up?(who had no history of cold sores)
by 6 weeks from infection, 70% of people who are going to be positive on the HSV 2 antibody test will do so.
4) how common is it for hsv igg antibodies to be completely undetected, and the chances that my boyfriend has had this the whole year of our relationship but only just transmitted to me when he had a sore?
The IgG test for HSV 1 misses 30% of HSV 1 infections.
5) if his igg antibodies were missed before, would it be worth it for him to get blood done again, or wait to see if he gets another sore to have it swabbed?
He could do another test, but it could miss it again (or it could have missed it in you, also). And yes, if he gets another sore, be sure it gets swab tested.