I agree this target date sounds extremely difficult.
As for your more general queries, not many of the jason experts are still around (except a few moderators perhaps) to explain why you usually end up in the 8000Ks in the research-based VCs (except if you're Drazek.) But I think it has a lot to do with the fact that those long-gone experts wanted to eliminate milking as the best way to win a GOTM. In the old scoring system (which measured only Firaxis score) and in some other models that were discussed before jason score was established, a good player could combine a slower VC (cultural, spaceship, diplomatic, histographic or "pseudohistographic," e.g. when a player milked to the year 2050 BC and then chose an arbitrary VC) with milking near the domination limit. The milking part would pay off to such a degree that if it were to be combined with a generous score for the VC-type also, then milking would be more or less a pre-requisite for a medal. I think we can agree that this was unfortunate. I don't think even you, me or the nestor above would still roam through this forum if the scoring system hadn't changed.
I hope I have given a reasonably correct historical description, even though I wasn't involved in the technicalities myself.