OP: I was you, for 3 miserable years. 21 years together. I have been gone three months. When I told ex he said "I won't make this easy for you you know", and he hasn't. But I still deal with him on a mainly amicable level (as best as possible), mixed in with his anger, resentment, bitterness etc.
Your head is a mess, your brain in a FOG. You know you need to leave but you are paralysed with fear. Start writing a list, write down why you want to lave and what is stopping you and work through the list one by one. Mentally or in a practical way. Two things prevented me from leaving earlier, one was guilt and a feeling he needed me and if I left his world would fall apart and worrying about splitting the kids and finances. I worked through not having the kids 100% in my head by deciding that they would be better off in the long run having us living apart. They didn't need to listen to their dad emotionally abuse me and treat me like shit. They didn't need an unhappy mother. They needed a mother who could focus on them, not focus on trying to tip toe around their father all the time and get the hair dryer treatment for wanting to go to the gym or burn toast. I was right about that one, better all round.
The guilt was a much tougher one, and I am learning still slowly, that it all boils down to how much I love myself. I decided I deserved better. I got myself physically stronger by joining a gym, and mentally I started to read and talk. Both have helped massively.
I really recommend taking a look at Lundy's book "Why does he do that" and also "should i stay or should I go". I wish I bought it 3 years ago not after I left but its helping me work through things. I get the reason from you is you are worried about his reaction which tells me he might be emotionally abusive. Can you tell more of what your marriage is like? It will help people try and see your situation.
I hope I am not off the mark here. 