I am trying to figure out what is going on here.. am I seeing it for what it actually is?

Anonymous
In the midst of a break up with long term partner, currently living in same place. I’m Trying to get out - rental issues in play at present so no immediate relief to have space as yet to process for both us.
Bbq on wk end for step daughters bday. Invited were close family & adult friends & child’s friends. No fights/disputes- which is a blessing. But there was some odd behaviour & mixed stuff going on from ex towards me. He is very subtle in how he plays out his behaviours or he is very loud in them. It’s one or the other.
When it was just his family and stepdaughters friends he was engaging and was joking and felt like flirtatious behaviour with me , trying to gain my attention but indirectly. He was like his normal self (like when together). He seemed happy & was watching me like a hawk, sort of taking me in if that makes sense. I was enjoying myself - the atmosphere was right. I was relaxed- I could be me. We ate before others turned up as we were starving. He lingers round the table grabbing food, indecisive where he should sit (the table is huge so plenty of room to choose to sit away from me) but he chooses to sit right next to me like he has always done. (Before this bbq he has been doing this stuff of hot n cold with conversation etc) one minute he seems mad next he seems sad next he is dissociating and or dismissive. He is really all over the place. He is normally very selective in who he spends time with , I have spent a lot of time in his company to know/pick up on these subtle things. His mood that bbq night literally changed with the lyrics to each song. Why would he be presenting like this? Then only when the adult friends turn up does he regulate his moods more and go straight to complete shut down but was watching everything I do and the actions/ conversations I was having. There were no extra males there that were single nor females- all were spoken for. It felt like sexual tension and emotional tension- it felt heavy. I don’t understand. Help?
I am trying to figure out what is going on here.. am I seeing it for what it actually is?
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