I think the chances of you getting HSV 1 from him using saliva as a lubricant are low. Not zero but low, especially since you’ve had no sores. You could get a blood test, yes, but as you said, you wouldn’t know where the infection was AND the IgG test misses 30% of hSV 1 infections.
I think your best bet is to quit hurting your back by bending into weird positions to see your genitalia and move along. If you get symptoms, get them checked out. Can you do that?