Correct. It's in the Coinbase transaction and since it's not a protocol standard, it can be a bit ambiguous, any changes in the transactions will alter the merkle root though I think using an extranonce makes it simpler.

The r and s values are 32 bytes each and located in the signature. If you want to parse it but I imagine that will take sometime, not sure what this can yield though. They're meant to be completely random under normal circumstances.