Is he acting jealous? If so, why?

He is about 35 and I am 23. He has two other male colleagues who fancy me (I'll refer them to Sam and Ben). There are times he seems to have acted jealous, but not sure whether it was my imagination;
• One time I bought a male friend in to have a coffee with, the man in question glared at him, kept looking over at us and barely spoke to me. A few days later he assumed that the guy was my boyfriend.
• On Valentine's Day he gave me a chocolate heart and he said to me "Did you get lots of presents? I bet you did"
• I bumped into Ben on Saturday night and he bought me a drink. Today I was talking to Ben about him buying me a drink - in front of the man in question. He barely spoke to me and almost looked pissed off.
• He jokingly encourages me to sleep with Ben and Sam.
• He jokingly accuses me of fancying Ben and Sam.
• He flirts with other women in front of me
• He has been quite mean to me in front of Ben saying that he doesn't fancy me. For example, told me he's seen better looking women than me, told me that he doesn't fancy me and "I need to get it out of my head". I replied saying I don't like him in that way, he said "good I'm happy you don't" - despite acting like this he has still continued to flirt.
• He invited me to come out with Ben and Sam and looked annoyed the next day when I didn't go.
•I have seen him sat with his friends and staring at me.
•He encouraged one of his friends to sit with me and told me to sleep with him.