Ask about the girlfriend, because some LDRs are fantasy relationships. Ask how many times he slept with her, went out on dates,seen each other in person. If it's a lot, then it's not a fantasy relationship. Beyond that, dating bosses is bad news. If you do date your boss, tell people about, usually with the right connection, and if it's a chain or something other, they will transfer one of you. It happens all the time. This will remove any headaches. Beyond that,this is an accident waiting to happen. For instance, other females. When you're work review comes up, if you get high marks, and other female co-workers get low marks, and they know about the fling, they'll be using it against you.
Little story, so my brother works at this failing company, it's so bad the Dean was having sex on company time, doing stupid with his girlfriend. One day they came out of the copying room together,my brother saw it, they got scared. But since the company was a joke, it didn't matter. Then new people came in, and they turned to my brother, 'is there anything we should know to fix our dire situation?' My brother told them about the dean. The Dean got sacked. It's a for profit college. So watch your back on this.
They had like three students show up just to keep up appearances...