I went as low as I could and I still get the same error. This is a premine wallet so the mined coins show and amount of 0.0000000. I have no other assets in the wallet, can I send a mined coin valued at 0.0000000?

I did a rescan and reindex but I still have the same problem,

Try re-scanning your wallet. Try this guide: https://coinguides.org/rescan-reindex-wallet/

Try transferring small amounts. If it works then you have many small inputs. You need to consolidate all of them.

Already tried that. In fact, as mentioned previously, i tried the instructions of…

“Instead of unlocking collateral using coin control feature there is also another method. First close your core wallet, head to your wallet file location and then open masternode.conf file. There you’ll find the entry of your masternode. You can either delete it or for future reference better add # in front of that masternode config line. Now restart your wallet and your masternode coins will be unlocked. You can then spend those coins normally.”

But as I said, no go.

I did that method because I do not have the…
“Go to settings >> options >> wallet and select “enable coin control features”
option listed in my wallet settings.

Again, how do i get my coins back? Please help.

Check this guide: How to disable masternodes and remove coins from it?

Even if you have coins in your wallet you don’t need to export private keys. Just backup the wallet. In case if you want to move coins from core wallet to other wallet in the future then transfer coins.