Firstly, though I disagree with many of your perspectives this is a well written blog.
I believe your concerns about energy production, specifically peak-oil, and its correlation to computer production are misplaced. Solar energy costs are now reaching parity with coal and green energy investment has surpassed fossil fuel investment. This is an important metric that demonstrates that fossil fuels are not the be all end all for energy production and green energy is taking over. The battery that Musk has released (when it eventually becomes affordable enough) will provide an avenue for decentralized energy production. An energy revolution is occurring as we speak that has the potential to create abundance and take power away from industry.
Plastics and metals for production are an issue, but recycling is getting better in many regards and alternative materials are constantly being developed. Crystal drives are be developed that don’t decay like magnetic drives and can be “grown”, nano computers that work on atomic levels are developing - slowly albeit, and each generation of chips are more efficient than the last. As resources are depleted new methods of computing will be developed accordingly.
The Outernet Project and Google (among several others) are developing ways to get free wireless internet across the globe specifically to address rural access.
Technology is a pencil, eye glasses, and many other things NOT digital; this point I think gets lost in modern debate concerning technology.
Lastly, your experiences with cognition are anecdotal and based on your personal behavioral patterns. I use the internet and a digital device very often yet I feel no need to incessantly check my email or Facebook or anything else. If I am depressed I will spent extra time doing mindless things online, but that’s no different than my offline behaviors.
I have learned a great deal of the knowledge I have accumulated through the internet, to the point that many of my current university studies (in economics and politics as a returning adult) just seem like outdated and rehashed topics.
I’m also a musician who studies lutherie, both are interests that require long in-depth attention and have long learning curves. Again most of my personal development in these fields has been enabled by the internet. Tools are innate, it is how we use them that matters. Some of cognitive challenges you mention are of course real and require attention and inquiry. However, I believe that predominately these are greater societal questions about behavior and conditioning less than they are about machines/technology forcing us to act in a particular manner.
In any case, the internet isn’t going anywhere. The resource depletion required for your scenario would also indicate a global food/transportation/medical/poverty/energy crisis that would make the lack of internet inconsequential comparatively.