I'm glad you have a name and a framework for what you are dealing with. I'm sorry you are dealing with it though.
I used to work with children with attachment disorders and their families, and I'm going to second the advice to make sure you're getting adequate rest and respite. Parenting is always a challenge, but attachment disorder kids often require deeper reserves of patience, unconditional love, and consistency. You can't have that for him without taking care of yourself too.
I think the resources already mentioned are very good - I especially liked The Body Keeps the Score. I also recommend Simplicity Parenting, with one HUGE caveat, which is that you should read it when you're feeling high in emotional fortitude. It's a very "keep what works, forget the rest" kind of book. Simplicity Parenting is simply about setting the stage for a home life that feels calm and secure. It's aimed at everyday parenting concerns, but I think it is good background for anyone parenting and the sections about creating patterns and routines are especially helpful for parenting kids with attachment issues.
I think working with a good therapist is essential. Also, depending on your state and what insurance your child is on, you might be able to access in-home behavioral support. Definitely ask your doctor and therapist if there are any resources like that you could access. The kids I worked with got 2 hours a day of in-home support to implement behavior plans and work towards behavioral goals.
Attachment disorders can be really rough on children and families, but kids also have a tremendous capacity for healing and growth. I hope you find some resources and a path forward that makes you all feel hopeful about that.