how long can I ferment in the fridge before I may cross the fate of my dough?
is what Reinhart recommends in most of his books. After that the dough might still be viable, but you are risking it.
.... how my white "fridge dough" recipe (as per Zoë François & Mark Luinenburg in "Artisan Bread in Five Minutes a Day") manages to be bakeable (and quite tasty) up to a couple of weeks after preparation of the dough?
that the temperature in your refrigerator is set low enough that the yeast goes dormant. Otherwise I have no idea how your dough could be palatable - let alone rise - after sitting in the 'fridge for a couple of weeks.
Different story if you are freezing the dough - which puts the yeast into dormancy.
Keep in mind that even while refrigerated, the yeast are still working - more slowly, yes, but still working - and thus the dough continues to ferment. After a few days even if the yeast haven't expended all their food (which will leave you with a pale looking pizza crust), the flavor of the dough is going to change noticeably - and not necessarily for the better.
and start digesting the gluten in the dough after a few days. the dough will become very extensible and lose elasticity; will spread rather than rise.
I believe they are largely responsible for the change in flavour and small after 3 days or so that Larry describes.
Adding rye makes it worse, apparently.
Adding salt retards some of this activity a little (I believe). There are a few good discussions of enzyme activity on this site that might be useful if you are interested.