From bitter experience OP, I would never conduct difficult conversations with anyone over text anymore. Texts are so easily misunderstood, and this causes the situation to deteriorate even more. However, if you find it difficult to talk to your parents, why not sit down and actually write them a proper letter or email telling them how you feel about things. Maybe ask them for examples of when they think you have been a bad parent, so that later you can judge whether they are right and perhaps you have overreacted at the time. It's easy for other posters to say cut your DS some slack, and to pick your arguments, but in the moment it's not actually that straight forward, and we can all benefit from hindsight. Although in saying that, it might be worth thinking about if there are any particular flash points between you, which really aren't worth fighting over, but do this when you're calm and have time to think it through properly.
I once had a problem similar to yours where my child was in someone else's house, the people weren't family, or even friends of mine, just the parents of her boyfriend. She refused to come home, and instead of backing me, as his parents should have done, they simply added fuel to the fire by stating that she could stay if she wanted to. Unfortunately, I was brought up to be polite, so instead of going in and grabbing my daughter by the arm and physically marching her out, I gave in and left her there. Biggest mistake of my life, as she then knew that she could go there and I couldn't make her come home, and in response to a PP's comment, the police would not have intervened in your situation, as I phoned and asked for advice, and was told that 'provided she wasn't being held against her will, and was safe, there was nothing that they could do'!
It really does sound like you're trying your best to be a good parent, and I know from experience just how hard this can be with teenagers, so if you need some support and would like a chat, please feel free to PM me.