Malak being above Sadow is a big no. He's probably not even above Kressh. And yes, I know you don't care about the order.
As for Nihilus, people who accept Traya's comments about a "mere thought" drawing him etc. will have to accept that he "may even rival the Ancient Sith", which means its dubious at most. Under that logic, he wouldn't even get past Sadow (and if it came to a strict fight, I doubt he would).
He probably makes it up to Exar Kun before his Drain fails him and he dies.
Nihilus's telekinetic feats are suspect, quite honestly. Assuming he did in fact remove his fleet from malachor's mass shadows with brute TK, he did so from an extremely powerful dark side nexus and under unknown circumstances. (Perhaps with aid from the other dark siders, a la dorsk81 and the Yavin iv?)
furthermore, the notion that he kept the Ravager intact with brute TK is contradicted by the fact that the ship retains its structural integrity even after he dies, despite the presence of (dozens? hundreds?) of individuals inside acting against it.