People have taken to giving these dissertations about why's and how's of Doublefine's internal workings and the development of that game but, at the end of the day, if the game is good enough when it comes out, people will forget (most of) their current complaining and enjoy it. If the game turns out to not be good enough, the current complaints will escalate to several times the intensity. That's really all there is to it.
In your post you make quite a string of assumptions:
That the second 'half' of the game WILL in fact be long enough and fleshed out enough to warrant 14 months of development (ie will be many times as long as have many times as much content as the first 'half')
That the puzzles in the second half WILL in fact be challenging enough, good enough and plentiful enough to satisfy the adventure game enthusiasts that comprise the majority of the backers of the game
That it WILL in fact be bug-free and polished to a level that warranted holding the game back for this long, ie no visible bugs or problems with the game almost at all
That the story WILL in fact be good enough and fleshed out enough without a rushed ending, or any filler or boring parts
Now the situation that DF has put themselves in is that they have to hit it out of the park in each and every one of the four points above with the second half of BA. If they stumble on even one of those, after all the delays and extra money they've gone through people will crucify them for it. That's just the reality the situation they have put themselves in.
If they DO hit it out of the park on all four, it's likely backers and people in general will be mollified and the complaints and general bad faith towards DF will markedly decrease. If you they don't, then the general distrust and bad faith people have right now will only increase.
Now personally, do I think they will come through on all four points? No, I don't, I expect they will stumble on at least one of them. But that remains to be seen.