I don't have time to deal with all of this long post but I want to respond to one part. You wrote:
- He wanted to phone his boss, but after thinking about it, the thought of going for a meal he considered preferable.
In my opinion, the first comma is in the wrong place. It should be after "but" so that the sentence reads:
- He wanted to phone his boss but, after thinking about it, the thought of going for a meal was preferable.
If you remove "after thinking about it", you are left with "He wanted to phone his boss but the thought of going for a meal was preferable" which, I'm sure you will agree, is a perfectly acceptable sentence.
Note that I find "he considered preferable" unnatural at the end so I changed it to "was preferable".
Interested in Language