7 year old with adhd- yep me too!
Ex who is abusive and uses screens screenshot convince the kids it is better at dad's house- yep me too!
One thing that worked for me was booking in the time when my son would get screenshot and would get, in your case, bike time. Putting it on a rota in the wall as a visual calendar. It means you have to stick to it. But rather than saying 'no screens today' i can kust say, 'you can di that at X time'
I also have a catchphrase of ' your big feelings are okay to share, but it is. Ever okay to hurt or damage things' over and over. 7 year old barely does that now.
Give options whenever you can- do you want to get dressed here or downstairs? Do you want a banana or strawberries? Silly little things- adhd need control so giving the control as much as possible with the smaller things really helps.
Lots and lots of praise. Any and everything I praise. By 10, an adhd child will have heard 20,000 more correctiins/criticisms than a non-adhd child. I was diagnosed with adhd last year, this is very true! Small negatives are massive to me.
Compromise- where you can. Explain about compromise and explain what you want, ask what he wants, reach a middle ground. But I explain that sometimes as the adult and mum it has to be my way. My 7 year old now doesn't react as badly when I do put my foot down.
It's hard, so I completely understand, especially with the added complications of coparenting... or having an idiot ex who causes more trouble than anything!