Thanks all, much appreciated. Will try the electrum verification route first as it was a real hassle doing the offline transaction safely last time so rather not have to do that again but may need to if the tx fees are too low like you say.
If you are concerned with security risks associated with creating/signing a second transaction, it may be best to broadcast your current transaction (assuming it does not violate any rules implemented in various soft-forks implemented subsequent to you creating the transaction), and use a Child-Pays-for-Parent (CPFP) transaction to effectively increase the fee paid. This will result in you paying more in total fees, but would prevent you from having to bear the risks of exposing your private key of your offline wallet again.