"I can see her behaviour as not great at mo but am having probs seeign it as being as bad as others close to me see it."
Armadillo, this is the absolute key here. I know you and I have conversed about this before and I have a good idea of how awful and controlling she is.
You need to make a total break with your mother at least for a time in order to be able to see how awful she is. Would you really accept this sort of behaviour from a friend or a work colleague? If the answer is no, then you should not accept it from her either.
Stop visiting her at her home. If she wants to see you, she can come to visit you. Your house is certainly not filthy. Do not obey her barking orders at you. Do not allow her to change your ds's clothes, do not keep toys/cots/high chairs at her home. Hang up the phone when she says she wants you to move home/visit her doctor/send ds to her local school etc/restrict phone calls to once a week and visits to once a fortnight. Her home is not your home anymore. Ignore your sister and father - they are not helping you.
My mother is bad, but not as bad as yours. And I have the same issues with siblings who also see her behaviour as "normal" because it is what they are used to, and a father who thinks life will be easier if we all just go along with her mad rantings. I am only now starting to say to them that I refuse to tolerate her behaviour anymore and only because I am married to an amazing man who has helped me see that I don't need to run to them with my problems anymore. That I should stop allowing them to control me. And, most importantly, that it is not in the interests of my dc to be exposed to her bad behaviour.
If your relationship with your dp is good, then get married. He is your ds's son for goodness sake - who on earth does your mother think she is trying to divide your ds from his father? Is that in the interests of your ds? No, of course it's not. It's in the interests of your insane mother.
Gosh, hope I don't seem too dictatorial. Just really want you to make the break from her. Your confidence will improve so much when you do. She has you thinking you can't invite people to your home because it's too filthy fgs! It's rubbish!