Question (#4) Is it OK that both the old wallet #1 and new wallet #2 are created in the same Desktop Wallet? In my case I'm am using Electrum.
the answer is yes and no,
yes it would be ok if you will never reuse the old wallet as a receiving or change address
no, there is a possibility of revealing the connection between the old and new wallet
if you are still using/receiving coin in the old wallet, you could accidentally join them in the next transaction
but if you understand how to use coin control, this can be easily avoided