Weird coworker vibes

[NEConfusion]

This coworker has been showing me attention in subtle ways for over a year. I started noticing him looking at me a lot shortly after I started working with him. At first he wouldn't really say hi. Our eyes would just lock for a beat. Hes very attractive so I didnt want to read too much into it. Our first christmas party rolls around and he makes a comment about not knowing me too well and didnt think I really talked much until seeing me out. He tried to bring me into a few conversations...teased me a bit and I noticed him listening when I was having conversations with other people.  Another year goes by and I can feel his eyes on me even more. He would say hi sometimes but not always. We would make lots of eye contact. Christmas  rolls around again and as soon as I get there he is like you never says hi to me. I just get a head nod from you. I tell him I do talk and he responds with "yeah here you do!" We joke back and forth about it a little and I tell him I am not much of a small talker. He says "well I'm not either with a smile". We chat a little. At one point I get up to get a drink and he jumps in my chair. When I returned he immediately offers it back to me.

For about 3 months after that, every time he would see me he would say hiiiii "insert my name", how are you?  Mid March i am in the office where he works, for a meeting, getting lunch in the cafeteria. I see him staring at me from across the room; looking over his hands. I smile and wave and he straightens up and smiles and mouths "hi".
I get back to my desk and I have a private work message from him about an hour later saying "hiii...it took me a second to realize that was you. I thought I probably looked creepy staring into space." 

Every time hes in the office with me he goes out of his way to say hi to me now. I am not anywhere near his office or in any necessary path for him to walk. 

Most recently, something odd happened. He is very good friends with my boss. I was having a meeting with my boss and he proceeded to tell me that i am very different at happy hour than in the office. I was taken aback and told him that was a social setting so I do tend to be more relaxed. He then proceeded to say you know if he (said guy) is busting your balls and you are joking around, you can do that here in the office.

 I ended up messaging the guy at work the other day to apologize for something that happened and he said  how dare you?? Haha i will give you a pass...this time.

I don't need anyone to tell me this is inappropriate or a game, or that my boss stepped over the line..not to s*** where i eat, etc. We are all similar in  age and speak candidly with one another.

Do you think this guy is into me in the least bit? I don't want to give him the green light if this seems like a stretch.