The initial concern is for your daughter. How would she be affected and her wellbeing ensured, financially and emotionally if you were to leave. Clearly your intention would be to leave her in the care of her mother, although you are equally responsible for her as her parent also.
If your partner has suffered awful trauma in her past, depending on what this has involved, it is possible that she has in some way been attracted to the qualities in you that you have described and sought therapy for, in that they are in some way familiar and normal to her, and therefore she may have learned and expected that love is painful, and you have fulfilled and perpetuated this cycle for her, exacerbating rather than healing the trauma, and leading to prolonged mental distress, and the possible depression, anxiety and stress.
It is possible that she was suffering from Complex-Post Traumatic Stress Disorder when she met you, and that this is now ongoing due to the nature of your relationship and the lack of support or recognition she has perhaps been provided by you.
C-PTSD can often be mistaken for other mental health issues as it can appear similar. It is likely that your arguments make this worse, and that in some ways your relationship, due to your inappropriate responses to her insecurities, have kept her in trauma mode. In order to heal she will have required empathy, compassion, validation and acceptance, as well as a sense of security in her home life. Partners who do not understand this, or the protected ways that she will have learned to seek it, can respond inappropriately, becoming defensive, aggressive, frustrated, and taking things personally, rather than better understanding the bigger picture.
Your partner will have developed a tremendous inner strength and resilience to have overcome the past trauma, and your current relationship. You both need to be honest with each other, and respectful, in that if you do not want to be with her, do not feel the compassion and empathy towards her that she requires, and no longer find her attractive, letting her think you are getting married now is inappropriate. You are not protecting her by doing this.
It is likely that the defensiveness and frustration and anger that you feel towards her comes from an expectation that she isn't fulfilling your needs, and rather than seek to find out what she needs to be content, you have been getting mad at her for not being content. She will not heal in this environment. The only way to move forward together would be for you to want her as she is, and then watch her flourish, rather than get mad at her for not being what you want, and then getting mad at her for shrinking.