Vowel shift. They happened all the time through history. Gradually and at times explosively.

Yes, but the real thing in English spelling's case is the combo of a radical change in phonology with a preservation of the old orthography. English is possibly the onlymajor European language to have not gone through a orthography reform in 600 or so years.

The dawn of printing. Do you mean that the introduction of printing made people more aware of language, grammar, phonology, syntax ? Was there clear a connection ?

The introduction of printing led to a standardization of spelling and an rise in literacy.

The etymologizing of... 'The tendency to preserve etymological features even after phones have changed drastically' means pronunciation and written word did not develop completely synchronic ? And in remote parts of a language region did and do not some old pronunciations stay on, just because they were less touched by the sweep of time?

Sometimes remote areas preserve archaic features that have been lost in central areas, but not always. Also, some work I've seen suggests that not all change is constant. Some linguists have used an idea from evolutionary biology in historical linguistics, that of punctuated equilibriums.

Dialects preserve old sounds.

Sometimes, but also sometimes dialects diverge while the standard language remains more conservative owing to spelling, literature, etc. especially, if like so many European dialects a standardized orthography is not available for the dialect.

Ceci n'est pas un seing.