As for the other stuff, if I cut those out I get miserable and more easily bored. Better to use them as carrots; "if I do 45 minutes of coding I can play 1 game of Rocket League."
In my experience this is temporary. It takes about 1-2 weeks for my brain to adjust to the "new normal" of not playing video games or binging youtube. These 1-2 weeks are quite boring, but after that I am able to find things I would normally be bored by interesting. It's as if there is a "boredness set point", and once you cut out the most stimulating activities, less stimulating things like coding or reading will become more interesting to you.
That said, I like video games and youtube videos, so I often go for a middle-ground approach like you.
Work time is for work, and after work I can game. If I need a break during work I'd rather just read hackernews for a bit. Less addictive :P