These first two sentences show никто split with a preposition:
Я ни у кого не был. (I haven’t visited anybody.)

Он ни с кем не говорит. (He’s not speaking to anybody.)

Applying this pattern I came up with the following sentences:

Я не обсуждал это ни с кем. (I haven’t discussed this with anybody.)

Я бы никогда не сказал такую вещь ни о ком. (I would never say such a thing about anybody.)

Are these last two correct? Also would ни о ком be pronounced with a long o for both о and ком? Thanks!