Basic STI panel, I guess. Idk how much they run these days. Probably depends on where you go (health department, planned parenthood, primary care physician) and whether you're insured or not.
So I read it as he only went down on her, that oral sex was the sex that they had.
If they had vaginal intercourse AND he went down on her, I suspect that like a lot of people they used a barrier method for the PIV but not the oral. People don't tend to think of using barriers during oral even if condoms are pretty normalized for PIV.
I suppose it can be read that way. When I read "we ended up sleeping together" I'm assuming everything was done. Barriers or no- I'm also assuming the same precautions (or lack of) were taken for everything