Child’s Aggressive behaviour

My 4.5 daughter often has violent emotional outbursts when I set a limit. She rarely has these events when interacting with anyone else. Not at school, not with grandparents, not with her father (my husband). She’s been doing this since she was about 18 m old. Biting, hitting, kicking, pushing me when I don’t give her what I want.
I recognize that I have let her bully me because I’m afraid of the pain of being hit. She used to bite my shoulder if I would pick her up to soothe her. It has lead me to believe I am failing at motherhood. I struggle to set limits or boundaries with her.
It affects every interaction I have with her. I have managed to foster a more positive relationship for a few weeks at a time but it inevitably ends up back in violent cycles.
With her being home full time, it’s been very challenging for us. My husband is constantly breaking up fights between us because she will allow him to sweep in and soothe her even though I’m doing everything I can to try to deescalate the situation. His reaction also leads me to believe I am not good enough. He’s constantly offering suggestions on how I could do it differently or how I created the issue. He’s always reminding me I’m the adult and she is the child so it’s up to me to make the change in our relationship.

When I try putting this into the model, I get stuck. A feeling is just a vibration in the body. Sure. But when she kicks me square in the face I feel /rage/. That feeling isn’t just a vibration. If I let myself feel it fully, not only will I continue to be pummeled by her fists and heels, I will lash out right back and defend myself. I have slapped her back a few times and it just sends me into a bigger shame spiral because I understand I’m not in my adult emotional state and I’m worse than she is. I am unable to model what calm behavior and emotions look like when I’m being hit. If I can dodge the blows I can be calm and patient and wait for her to settle (sometimes 10 min) but I can only take a few hits before I lose my cool.

Am I supposed to be able to think a thought that makes me less angry about being hit?
I’ve tried the opposite; let her hit as much as she wants and tell myself its just a vibration, it’ll pass.. but then I end up crying in pain which doesn’t stop her either.

I know this is a complicated. I hope you can help.