The answers you seek are in the Yellow Paper, Appendix F and section 4.3.
This means that for a normal transaction (not contract creation) the following quantities are signed:
- The nonce
- The gas price
- The gas amount
- The To address
- The value
- The transaction data
(optionally a new signature scheme involving
chainId is also allowed as described in EIP 155)
The only non-signed elements of the transaction are
s, "Values corresponding to the signature of the transaction and used to determine the sender of the transaction" - i.e. the signature itself.