I'm just dipping in here, will hopefully return later, so do excuse focusing on just one thing for the moment.
You've mentioned that your DP does nothing with any of the children.
With regards to the three older children, could it be that he feels somewhat powerless to influence their behavior and is therefore withdrawing?
Several times you have mentioned poor behavior at home among your older children, they are constantly arguing, never do as they are asked and you are unable to stay home at weekends as their behavior gets worse ... things like that.
You seem to think that's okay because they are good at school and lovely with other people.
Your DP doesn't seem to think that's okay, he think the eldest can do no wrong in your eyes and won't take DS to play football until he starts doing what he's told.
With the toddler, almost the first thing you told us was you practise attachment parenting, and ... while you do say you want your DP to help with her ... it does sound as if it is you who is controlling how things will progress. You're still BF and, despite agreeing with some posters on here that it would be best for the whole family if you stopped, I don't think you want to. She's still in your bed and as she wakes every 2 to 3 hours (every 2 - 3 hours, at 18 months old!), this must be disruptive for all of you ... yes, your DP too, even although you are the one who wakens with her ... all three of you, you DP and toddler, must begin each day exhausted.
Begin each day exhausted, as the three older children begin each day (hopefully) refreshed and all ready to start arguing again.
It doesn't sound as if you and he are on the same page at all, not even close, and ... as a result of that ... he is opting out of not only helping with the children, of interacting with them much, and of working with you to parent them, while you are doing more and more of the day to day care and becoming exhausted and resentful, while turning a blind eye to the behavior of the elder three and unilaterally controlling the progression of the youngest child.
It all sounds so frantic! I think you are both lost and feeling rejected, while at the same time being controlling and passive aggressive in your attempts to deal with that. I think you are very nearly not a couple, in your lives.
Obviously there are hosts of other issues going on, but taking the issues of parenting as a starting point, I suppose the first thing you've got to ask yourself is, do you want things to change? Change a lot. Even if that meant the you had to stop BF and co-sleeping straight away? Even if that meant you had to give your DP an equal say in parenting and had to agree (and stick to) house rules for the whole family, including and especially with regards to the behavior of the three eldest DCs?
I can see that he has a lot of changes to make, a lot of effort to make, and a lot of responsibility to take ... but you do too. Equally so. I think you've got to tell him this, talk to him, and listen.
And now my 'dipping in' post is nearly as long as your ..... 