Much of the framework of your experience is familiar to me, I've been dealing with it in varying degrees since around 2000 or so. When i was a kid I read everything I could get my hands on, and a lot of that love and energy for the written word eventually shifted to the online written word, with the added bonus of internet forum interaction. But - somehow, reading a book for three hours seems a lot more respectable than being online for three hours.
Over the years I've tried going cold turkey, giving myself an allotted period of time, creating different rules of engagement, and here's what I've learned about myself, and maybe something may resonate with you:
1. If at all possible, don't start the day online. Make yourself wait. Past your first cup of coffee, past your walk, your breakfast, your shower... wait as long as you can, because the minute you give in to that impulse to see if you 'missed any big news overnight' the wheels of your day's best-laid-plans are already grinding to a halt. If you work, wait until you're at work. If you don't work, try to make it the thing you do right after lunch. I promise you, your mornings will be so much more productive...
2. If you can, try a one-day detox. You'll be amazed at how different the day is, because a lot of us have forgotten what it feels like to be untethered from the internet. Think about how different it feels, really be aware of it. Revel in it even, if you're not too miserable.
3. If your one-day is successful (it takes a lot of self-control for me to make it through the day), make it a weekly thing. Full disclosure: I'm not there yet, but I've had some small successes and it's been encouraging.
4. I've dealt with depression. Speaking only for myself here, being online can be numbing, and there are many times I wanted to be numbed - the day was quicksand already anyway, right? As I've battled up one hill only to slide down into the next ditch, I've been aware that how much I was online seemed to be correlated with how well I was doing. I'm saying correlation because I don't know causation. Was I online because it was a already a bad day depression-wise, or was being online for hours a catalyst for a bad quicksand day? I don't know the answer to that.
I do know that being online changes your brain. The way you read isn't linear, like book reading. Your eyes move all over the page, looking at this headline, over at that graph or cartoon, up at that photo header, down to the comments... for many of us, our attention spans are getting shorter, too. We want everything quick, and a book that we might have been willing to stay up half the night reading now seems too daunting. Easier to read an article...
Anyway. Sorry for running on. I wish you all the best, count every small success as an encouragement to keep moving forward, and if you fall down, get back up and keep going until you find the best life balance for you.