I agree with your conclusion (this is a worthwhile pursuit), but I have some qualms.
There are a couple of general points that I think really need to be addressed before most of the individual points on this list can be considered seriously:
Following a list of prescriptions and proscriptions is a really poor way to learn any complex skill. A bad writer who earnestly tries to follow all the advice on this list will almost certainly still be bad at writing. I think the absolute best, most important advice to give to an aspiring writer is to write. A lot.
What constitutes “good” writing is a matter of taste. As with other aesthetic endeavors, it’s practically impossible to write tasteful prose if you don’t have taste in reading prose. I don’t see any real way to develop taste without reading a lot, and paying attention to what you’re reading and how it’s written. To some extent I think every person has to pick apart writing that they think is good and figure out for themselves the nuts and bolts of good writing. The resulting insights might be temptingly easy to distill into bullet points, but this is a very leaky process of abstraction. Most of the value of these insights isn’t really communicated in the summary, but is in the data in your brain that made these patterns obvious to you. It’s the A Monad is Like a Burrito problem.
Compounding the issue of taste, there’s the problem that “good writing” is an underspecified term. There are a lot of extremely popular and wealthy authors whose writing isn’t considered “good,” at least by those who seem to have taste. Is popularity orthogonal to “good”? Should our goal even be “good,” then? Or is maximal popularity not, in fact, our goal? I have no idea what the answers to these questions should be. Would I rather write like Nabokov than like Dan Brown? Yes. Would that be instrumentally useful in spreading my ideas (or ideas that I like) as widely as possible? I don’t know. Possibly not.
I have a few comments about specific points on your list, but I’ll split those into other comments.
Edit: Grouchymusicologist has already covered silly grammar-nazism, passives, and Strunk and White, complete with the Languagelog links I was looking for.
I think this one should be deleted. The first sentence of it is wrong as written, but the idea behind it is expressed clearly and sufficiently in #26 anyway. People do not talk in grammatical, complete sentences.
As for the second half, do you really look up etymologies as you write? I have only the vaguest sense of the origins of the vast majority of words in English, and this despite taking 5 years of French in school. This advice doesn’t look like it was actually meant to be followed in any practical sense, and I would need some convincing that it’s even a good idea.
This advice seems similarly quite arbitrary and unmotivated.