I don't know if your child is a RAD child - but at least there is comfort in knowing that there are people out there that know what you are going through. You need to surround yourself with support from others who have been through this. Maybe there are some strategies they can share with you.
Don't listen to anyone else who does not support you or says this situation is your fault and yours to deal with alone. It's just everyone else covering up the fact that they themselves choose not to help, so they guilt you into it so you can go at it alone - lets them off the hook. Don't listen to them and don't talk to them.
On googling on RAD strategies, I get some helpful pages:
Parenting the RAD Child: Reactive Attachment Disorder Parenting Tips Support for Parents and Caregivers
I am sure there are others.
I am not saying your child is a RAD child. But maybe if you seek out support (not judgment) you will feel better internally dealing with the stress of parenting your particular child.
In parenting, there is never a perfect parent. We all have times when we feel we can't handle it. Or we all have times when we feel like we can strangle our children. Say that out loud and people will prosecute you for your thoughts, even though you would NEVER act on them. There is so much pressure to hide our true feelings, fears, and not discuss them openly. That is a problem for THOSE OTHER people - not for you. So seek out those who feel the same as you and can discuss these challenges honestly and openly without judgment.
Good luck to you.