First of all discipline and love are equal parts of mothering. They are actually the same. If one loves their child they will discipline them to provide security, protection and guidance. the book “Dare to Discipline” helped me to understand this principle.
Second at this stage of his life, your son needs help to get on track before it is too late. I suggest you call this number, 855 382 533, explain your needs and ask for a referral. They are loving people who understand what you are going through and will offer good advice.
I am praying for you and your family. I am praying for the challenges you face as a single mom, I am praying for extra strength and wisdom. Blessings to you.

OP, I haven't read all the responses here but I wanted to offer my support.

Also, I have one child who is smart, extraordinarily sensitive, sometimes oppositional/defiant, very hard on himself, shockingly attuned to my emotional state, etc....

The work of Ross Greene at https://www.livesinthebalance.org/
has been PROFOUNDLY helpful to me. It gave me a new way to talk with my son and work WITH him to achieve what we both wanted. It takes effort, but it's really been (gradually) transformative for us. And it makes parenting feel much more achievable, loving, and successful when we're in the trenches.

Good luck!!!! You are clearly doing an amazing job. You're in the weeds right now but you and your son, will find your way.