To answer your other question, yes you can include a very small fee and it might take a long to for your transaction to confirm if it ever does. After several days, most nodes will forget your transaction if it doesnt confirm but it will remain valid as long as all the inputs remain unspent. This means someone may broadcast your transaction long into the future if it is still valid. This means you should keep your private keys, including backups if you ever even try unsuccessfully to send coin between wallets.
Wow, so there is no way to cancel an unconfirmed transaction even after say 2 weeks of it being unconfirmed? What happens then? How to get it on the blockchain later?
No there's no way to cancel unconfirmed transaction it will just be rejected by the nodes it is not likely the same as you make a transaction offline where you can just delete the transaction and make a new signed transaction.
Based on my experience before with Electrum my unconfirmed transaction for almost a week it gets rejected and the transaction will be gone in the transaction history. So if you don't have the raw transaction you can't rebroadcast them again but if you have a copy of raw transaction you can rebroadcast it.
Anyway, If your transaction gets rejected you can make a new transaction again as normal as sending. If you don't want the transaction gets rejected always check the recommended fee from coinb.in or bitcoinfees.earn.com Because if the recommended fee increases and you pay 1sat/byte there is a big chance that your transaction will be rejected again. That is why it's recommended to use the recommended fee from Electrum.