1. I give no shits if my answer is anyone else's answer. The only time it matters is when 2+ of us are discussing the thing. I'll start paying attention to how many types there are "objectively" when the science behind it matures enough, but even my great, great grandchildren will be dead by then.
2. With respect to Judging Fi'ers and so on -- seems to me that it's a matter of what's actually of use to represent in a model. Do we need to differentiate INFPs who have Judging tendencies from those who don't? Yeah, it's a worthy idea if there's a huge variability within INFPs (and other types) that can be explained by introducing it. Do we need another whole dichotomy to tell us whether a person likes to dip their fries in ketchup or not? No, but we could do that, too.
Kinda-sorta like how the Japanese color "ao" doesn't differentiate between blue and green, since a distinction wasn't seen as necessary. (Similar with a lot of other languages, too.) Separating the two introduces more complexity (one/two additional words) but it's worth it if distinguishing between blue and green is useful. Is it useful/necessary to subdivide green into, say, neon, xanadu, lime, olive, forest, jade, etc.? For everyday use, probably not so much.