Morning,
I need some advice please 
Ex husband and I have been divorced for about 3 years. Divorced because of his unreasonable behaviour (gambling addiction and he pushed and bruised me when I was heavily pregnant which he accepts but says it was my fault because I made him angry) his girlfriend read our court papers and is pressuring him into marriage and kids apparently 
we are both 25 and I have two girls with my fiancé now. My ex has been in and out of my sons life since we split and originally we arranged that he would see our son every fortnight. Soon after that got less and less. He's in the army so I can understand the work side but not the holidays, stag dos, parties and so on. He's constantly giving excuses about how he has no money to see him but when he first started saying this we lived less than 5 miles away in the next village but had the money to drive an hour and a half away to see his gf every week.. This year he has seen him only a handful of times if that and a few months ago he said that he doesn't want to be a dad and could he hand his parental rights over to my fiancé. So I explained what that would mean and the process and he was adamant he wanted to go through it and said that it was in the best interests of our son. I spoke to the social worker for step parent adoptions and we got the ball rolling. He's in Afghanistan now and yesterday he sent me a message saying that he doesn't want to go through it anymore and that he misses him which is fair enough I guess.. then he started saying I make him feel like a bad dad and that he can never do anything right. All I want for our son is the best? It upsets me that our sons behaviour goes downhill for a few days after he's seen him. He doesn't speak about him anymore and he's so confused when I try and explain about daddy. He's in and out of his life and provides no stability. He puts his needs before our sons and says that he's entitled to a social life etc. When our son was in nappies he used to come home with the same amount and a huge wet nappy with nappy rash. Bringing him home wearing wet clothes after jumping in fountains in London and it was dripping., I regret not getting legal advice at that point.
Child maintenance had been quite difficult with him. When we agreed on how much he would pay he ended up giving excuses every month so I went to CMS and they sorted it. When we went through with starting the adoption process he said he doesn't want to pay cms anymore so I could kind of see his point seeing as he wasn't going to be around anymore. During yesterday's discussion he mentioned that he can't pay cms until February and he would backdate it but he's said this before many times so this is why he got cms in the first place because he doesn't keep to his word. He called me a c word and was saying how horrible I am to him. I don't intentionally mean to be? I just want what my son deserves.. he also demanded that he will have him one weekend a month (from Friday to Sunday) and he said that he can do this because he has as much rights as me. He expects me to take our son an hour away (about half way) to meet him once a month and My partner works a way a lot, I don't drive and I have two other children.. I said to him that I don't think it would be fair on our son to go from doing an adoption and saying he doesn't want to be a dad all the way to a 2 night stay at his girlfriends flat roughly 100 miles away once a month? He also has been attending a stage school every Saturday and thriving with that. He has a great routine and since starting school he's been doing fantastic. I said that we should start off small steps and once there's an established routine of him seeing him properly we can talk about overnight stays.. so now he keeps talking about his rights and what is going to happen. I don't really know what to do because he doesn't have our sons best interests at heart at all. Our son barely even knows him and he's only met his girlfriend once? I also feel uneasy because he's mentioned on numerous occasions about signing off from the army and moving to Cyprus and having him abroad and it wouldn't surprise me if he tried to keep him to be honest. So me and my fiancé feel quite a lot of strain and emotion right now. He's also mentioned that he will be definitely signing off from the army when he gets back from Afghan and that he won't be able to pay any cms and will get his gf to pay for him to come see our son.
What do I do?