Hi Rose,
My heart goes out to you. I thought I might share with you a little of my story because I do relate to your thoughts and feelings that you've written here.
As one who left my husband several weeks ago. We are relatively newly married - I'm not sure whether it makes it more difficult or easier than if we'd been married for eons, or just different - and I am 24wks pregnant with our first child.
Like you, I was initially fearful of being alone. Until that point, I had chosen to live with him in a life of misery in preference to being alone. Now, looking back on my weeks without him, I would choose being alone to choosing the life that I had with him before this. That is SO sad - even as I write this, it's terribly sad and disappointing for our young married life. But life was not only miserable, but it was not peaceful - and I am relishing the peace that has been restored to my heart and to my home. And I am beginning to feel more like the person I used to be - rather than this person I was beginning to loathe, caught up in heated dramas, chaos and arguments that seemed to be our daily life.
His daily choices still affect me, but not nearly to the same degree as they used to, of course. Setting boundaries with him has made me become the "bad guy" as you put it - and that has been difficult on the one hand. He is good at trying to make me feel guilty for setting boundaries, and I am good at taking the bait. Until I realised that by not setting boundaries, I was not loving myself, not loving my baby and not loving my husband by allowing him to continue the way he was without any real consequence. In fact, I was perpetuating the problem - almost being party to it. Setting boundaries with my husband has made me feel stronger, and has given me self-respect. Surprisingly, I feel my husband's respect for me has also grown - even though he plays the guilt games with me still.
I don't know if any of that helps, but please know that you are not alone in this journey. For me personally, I have surrounded myself as best I can with support after separating from my husband. I could not continue without that support. I would recommend that you work on that and put as much in place as you can before separating. Support may be in the form of close friendships/family you can see on a regular basis who know about your plans and will support you in it, Al-Anon, a support group, a counsellor, a church group, seeing a sponsor...
Keep us in touch with how you get on. I personally would like to offer my support seeing as we are in a similar place in our lives. Please feel free to message me personally, I'd be happy to be there for you where I can.