I don't understand where he's coming from!

I posted my sorry situation on the Broken Hearts forum so if you want the gory details you can go and find it there.
A quick overview. I'd been with my ex-partner for3 years and we have a one-year-old child. His parents pamper him and when we moved into our house they drove me mad by coming around constantly moving my things and complaining that things weren't tidy enough. I finished things in the hope that he would realise that things had gone too far and the little issues were now big things. I tried to patch things up a few days later and ex wasn't interested. He said he wasn't happy anymore and we needed 'time apart' to fix things.
From a guys point of view I'm just wondering what you make of the following things. We have now been apart a month and a half. The first week I did all the usual pestering and begging. Second week we had minimal contact. Beginning on third week ex starts making suggestions to 'hook up'. We go out on a date and it's very nice but he's being sort of cocky and not sweet like usual (he was like that before we got together, a lads lad). We talked about the issues and he said it helped but didn't fix things. We took our son out together in the second week of splitting. He indirectly invited me and then the next day decided that I had invited myself and he wants the time he spends with his son to be just him, not me.
Anyway, 2 weeks ago he texts to ask if I would like to go for lunch with him and our son. We had a lovely day and he was cuddling me, squeezing my shoulders and telling me I was "the old me that he loved". He also sent me texts telling me he loved both me and our son.
Then he went on an all weekend bender as he is on his 'holidays' from work (all his colleagues do it, it's happened every year). I had moved back my mums cos things were bad but I had an arguement with her Monday night whilst ex was out partying and I text him to say I needed to stay back at our house for a few days. He said that was fine. He comes in at 6am Tues morning and goes straight to bed. Midday his mum turns up and starts having a massive go at me saying that all his family don't like me and I need to get off my high horse!
Ex makes his mother leave and then says he's going for a drive. I don't hear from him all night. He doesn't text to ask about seeing our son til Friday (this started on Tuesday). When I say that he hasn't text he says: "You didn't either". Everytime I mentioned me and him he just stops replying. Last night (Monday) he finally texts asking if I'm ever going to let him see his son. I said I have never stopped him. He is the one who randomly stops replying to messages. By this point I had decided that all the lovelyness the week before was obviously gone and he no longer wanted to work on our relationship. I told him he could see his son today expecting him to reply "ok".
Instead he started sending me messages accusing me of going out on the 'piss' and messing around with people. This is because I am going on a night out for a friends birthday and we are staying in an open dorm. I told him he had changed and he said I had as well and I'd pushed him away. I told him about the situation with his family and he said he tried to be supportive but all the things I said about his family became too much. Eventually he sent me a message saying he just wanted to see his son. I told him he could come and see him today and discuss things (it was 1am when we sent these texts so not a great time anyway).
What do you think he is thinking? Does he want to work things out? Is he confused? I don't understand why he would attack me about the 'going out' if he wasn't bothered about other blokes. Was all the nice things the other week just fake? I don't understand how he can change over night because up until the arguement with his mum he even said that morning that he wanted to work things out. What is going on?????

Honestly, I'm not a guy.. but seeign as you have a kid and he seems very unstable, I think you need to not think about yourself, and what you want, but think of that it's not good for your child to have parents that are so unstable all the time. I am not saying this to be mean or anything, but children need stability. They need to know where they stand, and mommy and daddy too. He might be a bit too young now yet, but soon he'll be able to notice more and more. So have one good chat with your ex, tell him you're choosing your child, not him, and that he can cooperate or not.. set days for him seeing your son. If it's possible I would recommend him seeing his father regularly of course. I don't know how it works legally, since you're not married are you? Anyway, I might make some enquiries if I were you.
And just to say, hsi parents seem like the parents-in-law from hell, not good.