What you are doing looks correct.
Basically, if privateFor is missing, then the transaction is public. You must specify privateFor in order for the transaction to be private. All the nodes specified in privateFor (plus the local node) will become participants in that private transaction.
Any attempt to access the contract, or the state, from a non-...
Private ethereum blockchain is having an ethereum client running in local mode with non-default configuration of ports and connections. Otherwise it behaves and acts like a regular ethereum node.
By contract, Quorum private blockchain offers a set of services that is not available in a regular / plain vanilla ethereum blockchain. These are:
Privacy -- in ...
You need to increase the transaction data size, not the code size. The transaction data size can be increased on Quorum with the genesis txnSizeLimit value (up to 128kb).
This is documented here: https://docs.goquorum.consensys.net/en/latest/HowTo/Configure/GenesisOptions/#configurable-transaction-size