Have you sat down individually with one kid at a time and come up with a compromise? As a parent you are in charge, I couldn't agree more, but we also need to teach a 15 year old about self regulation and that somes things must be done (chores, homework, etc) and screen time is fun but not everything. Start with one thing, not a whole list, share that topic with them and set a date/time to meet about it. At the date/time, Share what you think is suitable, let them share their view uninterrupted, come to a reasonable compromise. They then have more ownership, you both share your views calmly so everyone feels heard, jt will support you by not having a constant battle or your fear of losing your kids while they run to dad's. This will then also develop your relationship about open and honest conversations. They will feel safe with you knowing you'll listen and it will feed out to other areas.
Once one thing is cemented, offer for your child to raise something that matters to them, and you also bring a topic.
I would say that some things are non negotiable; medicine, contributingto house chores, etc, that is a parent's job to decide. But if you can give that element of control to a teen/child in ways where possible (say screen time) then it helps counteract the parts of life where what mum says is happening, no discussion.
I do feel for you having the running to dad situation. I work in a secondary school and have realised that kids/teens like and need boundaries, but also want to have some control/say over their life. But they also need to understand that parent's, future bosses won't always give them what they want exactly how they want it.