I was also thinking about the guilt. I feel so guilty leaving a man in his 50s alone.
OP, this is how this happens. You are a decent woman, a gentle considerate human being. This is important, because what has happened to you actually hinges on that huge capacity for empathy of yours.
You are married to a sub-human monster. You are trapped and are sexually assaulted on a regular basis. Because you are a normal decent person, you block your feelings of outrage and anger. You go numb. You cannot actually process something so painful.
This is perfectly normal and usual.
Later, after a period of time, you have to also block the fact that you have blocked your feelings, because you feel that there must be something terribly wrong with you that you didn't react as a normal person would. You didn't object and you didn't run away, so you feel deep down that something is very wrong with you. You are numb to yourself and you cannot really contact anything about how you feel. You feel a sort of distant anger, but it doesn't - quite - touch you. It just sort of washes past you.
This incidentally is also a perfectly normal response to abuse.
You are still a decent, gentle, lovely person. You have a huge capacity for love. You cannot feel anything for yourself because inside you are numb and quite convinced that you are broken, weak and abnormal. So you forget yourself and begin instead to direct all that love and compassion inside you at your partner. You focus on him. You can finally feel something here, feel for him, feel for his difficulties and problems. So you do this, you care for him. All that gentle love and compassion that you cannot feel for yourself, you feel for him instead.
This is the killer point.
Feeling HIS pain, caring about his comfort - whether real or entirely imaginary - really helps you feel better about yourself, because you finally become someone that you are not angry with, someone that you do not loathe. Caring about him allows you to finally stop being disgusted with yourself. You can bear to be a caring, empathic, thoughtful person who puts someone else before herself. It starts to be the only way that you can feel better about your situation.
It is your only way of coping with appalling abuse and it is very common in this sort of situation. You are protecting yourself the only way that you possibly can.
This is the really saddest point about this whole sad process of losing your boundaries to an abusive partner. In order to be that lovely, gentle, caring person that you truly are, you have to feel all that love and compassion for the completely undeserving, evil sub-human rapist who is abusing you.
You can read the responses on here that caring for him is abnormal etc etc, but you know all that. You know, and you are deeply worried that you are also a monster, but you are helpless because it is your one and only coping mechanism. You NEED to feel compassion and concern for your abusive partner and you NEED to completely subjugate your real self in order to do so, and you will allow the abuse because it enables that need. Without it you fear that you would spiral out of reality altogether.
This is perfectly normal and usual in cases of extreme and sustained abuse.
You are struggling to transfer that need of yours to feel compassion to your Mother, but your partner is right in front of you, and with his overriding need to keep you where you are, accessible to his abuse, he will easily find a way to keep you focussed on his needs.
So here you are. You probably need some quite specialised help to unscrew your head - and trust me, there are professional people who completely understand where you are and how to help - but for now you need to just get to a place where receiving help is a possibility. The first important step on the journey to your wonderful future with your little son.
I want you to imagine that you have a grown daughter and that she is living with a partner who treats her the way you are being treated. Or perhaps imagine your Mum's desperate sorrow and anxiety for you if she knew the full truth of your relationship. Just keep imagining that. It will help you to see exactly what is really happening. It will help you to feel what is so deeply buried, your true feelings. Inside you there is a growing anger, a righteous wrath. It is a little flame. One day it will light you inside with such love and compassion for your poor, abused and generous self. You need to protect that flame and help it grow.
Then you will be able to walk away.