I have five now grown DCs.
I let them watch TV any time they wanted to, and use the computer. Oldest DD had a TV in her own room from age 11 or so.
Mine loved art, reading, and they played outside a lot. They also loved TV and thanks to access to PBS children's fare and other PBS educational nature, travel, cooking programming (in the US) they learned a lot. They also watched commercial TV on Saturday mornings - kids' programming on one station, and they loved The Simpsons. We had DVDs and video tapes too - we were early subscribers to Netflix and also rented movies from other businesses that got rolled over by Netflix. I bought DVDs and video tapes - memorable ones were Beatrix Potter animated stories with an intro featuring Niamh Cusack, but there were many, many others.
You are sending very, very mixed messages with your complicated schedule of viewing allowances, taking away viewing time for fighting, not listening to parents, etc. I don't know where to start on the bribery with something you obviously think is bad for eating fruit and veg.
Screen time is apparently so bad it has to be rationed, and yet good behaviour results in getting it. Have you sat down and thought this through at all?
I sincerely believe that if you make 'screen time' into forbidden fruit you whet their appetite for it. You also accord it more power than it really has if you treat it so seriously. It's not an alien force invading your home unless you choose to accord it that position.
There is an alternative - watch whatever your DCs are watching and chat about it while it's on and afterwards, the same way you would ask questions and make the odd little comment to see if your DCs are listening or understanding when you're reading a book to them.
And make sure you sit down and read plenty of books to them, talk to them about drawings and paintings they make, and invite them to share their thoughts and feelings on everything they notice and everything you point out to them each day.