All good questions John,
And the answer to most of them is that we just don't know for sure
1.There's tons of information out there on Fisetin at successive low doses, but that will not clear SCs. Successive high doses will, but I think people are overestimating how soon a second dose would be needed under ideal circumstances.
2.600mg is probably the bare minimum for removing SC's based on the study we are trying to mimic. I don't know where the 20-50% figure comes from but if that can be achieved it would be great. I would say at that low a dose 6 months may be appropriate. But then why not 1000-1500mg and only once a year, which will be my plan.
3.There is no need to fuss about residual SCs. Young people have SCs too, it is only the excess SCs that start to cause problems. There aren't going to be any hard and fast numbers, you just have to make educated guesses. If we could develop some metrics for how many SCs we have, then how many have been removed, it would change everything. But I don't see anything out there that's feasible at the moment. Even a rough ability to measure SASP would be a game changer here.
4.Don't quote me on this but I think that SCs are somewhat heterogeneous, although the differences don't seem to matter much for clearance purposes. Most senolytics have done a pretty good job of getting a lot of them removed at least in some tissues. There are cells characterized as quiescent, which I think are somewhere in between a viable and SC. Who knows if these are targeted or not. For humans, this is still more art than science.