As complicated as can be

Let me start by saying I've been in a relationship for roughly 6 years. We have 2 young children together and he has a child from a previous relationship (my stepson hasn't seen his mom since he was 2 and he will be 15 this summer. there is no relationship between him and his biological mom but there is a beautiful relationship between the 2 of us). My boyfriend and I recently signed the deed to a new house and both work full time jobs. My relationship feels as though it is in a stagnant mess. My boyfriend no longer makes me consistently happy. I understand relationships all have problems but at this point we have had the same problems for a long time and in order to correct these problems my boyfriend would have to face some hard demons which I don't think he will ever do. I'm slowly starting to come to terms with that last statement. I don't know how to walk away from this relationship though. Between the new house and our 2 kids it makes things difficult and then throw my stepson in the mix I become lost (I have no type of legal custody or guardianship of him). My biggest fear is if I go what happens with all 3 kids especially my stepson. And what about the house? Should I stay in this toxic relationship ship? Or should I go... and if so what is the smartest and safest way to leave in terms of the children and house? I can't leave without knowing my stepson will still be in my life and his siblings.

How come you and he were fine about concreting-in a marriage (producing kids) that hadn't even happened yet? Isn't that a bit cart-before-horse? How come he didn't propose first? How soon after meeting did you and he move in together? Why don't you think he 'ever will do'? So you do WANT to walk away from it? 'Difficult' is the bed you chose to make and now are lying in. Can you argue with that statement? But how come you waited until after something as majorly life-affecting as signing the deeds to realise this? Don't you think things through before you act? Wait up... Now this relationship isn't just stagnant but all of a sudden actually 'toxic'? Describe the 'toxicity' in detail and tell me what makes you believe your boyfriend would use his own and your shared kids as baseball bats to hit you over the head with? Huge anger and resentment at your lack of foresight as allowed him to commit himself to a house that he'll have to sell or part-rent to a lodger 5 minutes after having only just moved in? Or is he ALREADY treating you badly? Again - describe the ways, please.