The first one fails terribly. I've had dreams where I've thought I've proven some statement I'm thinking about and when waking up can remember most of the "proof" and it is clearly incoherent. No, subconscious, the fact that Martin van Buren was the 8th President of the United States does not tell me anything about zeros of L-functions. (I've had other proofs that were valid though so I don't want the subconscious to stop working completely).

The second one seems more viable. May I suggest using something like electromagnetic stimulation of specific areas of the brain rather than deliberately damaging sections? For that matter, the fact that drugs can alter thought processes not just perception also strongly argues against being a brain in the vat by the same sort of logic.