Does anyone have a source for the 'faster, more intense' thing other than the making of TPM? I really would like to know.

He could also likely sense Maul in the Force and feel the dark side swarming around him; he did, after all, have reason to turn around and warn Anakin despite being turned away from the approaching Maul at the time.
'Force sensitive darksider' is not the same thing as Sith, though. By rights he should suspect Dathomir.

Yaddle was on the Jedi council, but that doesn't mean the species is especially force sensitive any more than Obi Wan and Mace being on it does. The baby being capable of it, on the other hand...