Thanks everyone, for your replies.
Izzy, I came back to this last night, read your post, and couldn't face responding to it at the time.
I don't understand why you've had to be so spiteful in defence of a man you do not know. Things like "the OP is set on having her way" is bizarre IMO. Should I be set on having his way then? Are his needs more important than mine? Do I have to continue in a relationship that is unhappy because he doesn't want to move on? Is there a compromise that I'm missing here?
The rest of your post doesn't warrant a response that won't be deleted anyway so I won't waste anymore of my time either.
Math, I'm with you now. Thanks for your posts.
Balia, your rephrased paragraph made me wince for the right reasons. Thank you.
BoneyBackJefferson. I've advised men to leave as well, but none of them have taken their children with them. I think the parent who is going to have residency should keep the home, where possible. That is non-debatable in my situation. DP does NOT want residency, which is good because DS wants to stay with me.
Garlic, thank you for your support 
Creighton, I've been thinking about your question all night. I hope single life will be a much less stressful version of my current life. These are the things I've avoided posting about before because I don't want to paint DP in a horrible light, or make myself sound even more of a bitch.
DP was retired on medical grounds a few years ago. He was always a bit of a misery guts but having to now live with it 24 hours a day is unbearable for me. He wants to be joined at the hip; where I go he follows. I cannot even chat to a neighbour without him coming to find me. It is stifling. He is content with a life of watching soaps/game shows, doing jigsaw puzzles and playing on the xbox. He has the opportunity to retrain for a job he could do/would enjoy/pay well, but he won't do it because it requires mental effort. I am tired of listening to day dreams and fairytales. I have had enough of it and don't want to continue. I have told him he needs to find hobbies/work outside of the home for both our sakes, and he agrees and then does nothing.
Single life might be shit, but partnered life is definitely shit when your partner is a like a surly teenager. There is nothing good to salvage, for either of us.
I've got to think more about what single life would be like though. At the moment I'm focussed on ending this misery and the rest is just fantasies about a baby. I can't imagine myself even being naked in front of another man so a new relationship isn't a motivator.
A few other things. DS is 10, not 15. I didn't mean to imply he was conceived so early in our relationship. I suppose he was a bandaid baby. Stupid thing to do but he's the best thing in my life so I'm glad I did it. I'm sure DP is too.
DP and I spoke again last night. I've told him he has 6 months to move out. I thought that was ample but he thinks it's too soon. We have debts to clear and I want DS to get used to not having his dad around so much (he's retired so at home all day). We're sleeping separately now as well, so no more sex.
Sorry for mammoth post. I could go on and on though.