The mnemonic phrase is a seed that all the private keys and addresses for your assets in a certain wallet are derived from.

Yup, and your mnemonic for Exodus wouldn't work for other apps (I'm pretty sure).

You can go to your exodus wallet and navigate to a certain coin, then on the three dot button you can find the "show private keys" option.

I don't have that option for any of my wallets. Can you check to see thats still an option? Maybe Exodus removed support for it?

I can't help with your 64 char string.

I'd suggest contacting Exodus support, or ask on the Exodus subreddit. Maybe try contacting Exodus via Twitter.

Good luck mate.