RBF activation and deactivation option is available in Bitcoin Core.
If I transfer the private key to Bitcoin Core and disable the RBF option from there, will there be a definitive solution if I start the transfer process from there?
There is no guarantee for such transaction that private key will be leaked in less than a minute but you have to do disable RBF and set highest fee for your tx.
You haven't found the key yet, what are you worried about !?