Welcome to the forum!
For your first question, it depends on where you leave them... if you leave them in the lactose rich whey, then yes, that is fuel for the cultures to do their thing, but as for fuller flavor, not necessarily. Flavors come primarily from the milk and methods of making. The cheese will be more acidic the longer you let it go, but that may be all that it means. Let it go too long, and the cheese will be sour from over-acidification. If you make wine, it is the same concept. Wine lacking in acidity will be dull and "flabby", so you add some acid. After you reach the optimum acidity, adding more acid will only make it worse.
I don't know about crottin, as I haven't made it.
If you can't get the right acidity, there may be a few problems. Not enough culture could be one, but this is not usually the case, and it is problematic adding more than recommended. It can mess up the whole sequence of steps. I think you should try other variables such as temperature and time. If it gets too cold, the cultures might slow down, and too hot and the cultures may work too fast, and hotter yet you might kill the cultures.
2c isn't that big of a temperature fluctuation, so I wouldn't be overly worried about it. I would assume that you'd want to keep it for closer to 18hrs as the warmer temp will encourage the cultures, but again I haven't done a crottin.