Satmar does not have 250,000 chassidim. I have seen a figure of 100,000 mentioned – I think even that is a bit exaggerated, but closer to the truth than 250,000. I do think Satmar is the biggest, though.
I think shein is pretty close:
“Satmar, Bobov, Ger, Vishnitz, Munkatch, Lubavitch, Breslov, Skvere” in that order. However Klausenburg also fit in somewhere, I’m not exactly sure where (depends on also on whether you count them as 1 or as 2 groups I guess). Same goes for Vizhnitz.
Chabad should not be mentioned in one sentence with the rest of them, really – they are not chassidim, but a sect.