I am wondering if I should stop leveling thought control.
You should stop levelling Thought Control at 75, because that's the minimum you need to get Locus of Control, and if you're playing a psi character, you should have LoC. Going even one point beyond 75 is generally a waste of points, even on DOMINATING difficulty, because not only will you only very rarely get resisted, but generally because TC abilities are so very short-range, you'll have used Premeditate+LoC to get an AoE effect at a reasonable distance from yourself and will thus have all your AP remaining for the turn to handle anyone who happened to be lucky enough to die by other means rather than by mind melting.
That said, if you want to go higher, by all means do so. Psi is powerful enough that there's no reason you should worry yourself over min/maxing.