Arg.. I just spent a half hour writing a long comment on this article, but then Chrome crashed when I hit "submit". I'll try to briefly retype my thoughts here since you've covered some of them.
It's quite clear that Boris did not want the referendum to win. While (like all tories) he would occasionally grumble about Brussels nobody considered him anti-EU during his time as mayor.
He was, however, obviously after the top job. He would upstage Cameron every chance he got.
When he decided to switch back to being an MP, Cameron brought him into his cabinet (without a formal position) He knew he had this referendum campaign to fight and having the popular internationalist by his side would help him command as much party loyalty as possible.
Boris then immediately pirouetted (bad mental image, that) and decided to lead the "Leave" campaign instead. The grassroots (largely Euroskeptic) tories who will pick the next party leader would appreciate his help. Cameron already announced that he would leave before the 2020 election, so this would mean PM Boris probably in late 2018/early 2019.
So the best result for Boris would be a narrow referendum loss while looking like a great anti-EU warrior. A lot of the rhetoric he employed was to this end -- when he would compare the EU to the Nazis, it would make him look fierce to the hardcore Euroskeptics who controlled his future, while whispering to the electorate-at-large that the whole Leave campaign was nutty.
It didn't work. He got what he nominally wanted, and now he has the chance to be PM faster than expected... but he has to deal with the fallout from this disaster.
If Cameron had invoked Article 50 immediately then the rest of the party would blame a sloppy exit on him... "we had a great plan to pre-negotiate everything, but Dave messed it up!" He's not giving them that option: if the country is to be destroyed, he wants them to pull the trigger.
It's startling watching the "moderate" Leave wing falling over themselves to dial back all of their promises during the campaign.... turns out there isn't more money for the NHS... of course there would still be free movement of workers from EU countries... maybe if Scotland doesn't want to do it we should call it off to preserve the union.... etc etc.. In victory, they're terrified of what they've done.
Of course, to the far-right any wavering will be seen as treachery. A fight is brewing there.
Meanwhile, Labour is also in full self-destruct mode. Corbyn just sacked the most credible member of his shadow cabinet and many of the rest will probably leave in protest. There have been many times in British political history when the out-of-power party goes through this sort of process, but never when the governing party is also in such disarray. Interesting times, unfortunately.
I don't know if UKIP will disappear, though. They could now be the party of northern grievance, locking Labour out of power entirely.