The interest on your deposit doesn't get added to your CD like 90 day deposit it gets added to your wallet. Because you need a minimum balance to earn interest this money just sits there. You can't really sell it unless you cro token unless you have at minimum around $100 for us stable coins and around $54 for mco coins. I tried to arbitrage dai when it was trading at 1.04 for usdc. The coin is advertised as being illiquid on the exchange and I probably have a small loss on the deal.
The credit card deal is fairly good at the 50 mco level if you enjoy music you can get Spotify for free and if you use a referral link you get $50 worth of mco. The exchange works better with larger amounts. Most likely you are not after better credit card rewards for locking up 500 mco but you will get a 1% and 2% on thier earning platform along with 100% on netflicks. If you are investing 100 grand or so it's probably a no brainier. Since this is an uninsured bank it's buyer beware though. Plus the stable coin interest could probably come crashing down if there was a huge influx of cash into it.
There is a charge for removing crypto but it can be done. If you are already have an account gaining interest then it could be worthwhile to deposit your small bat and dai tokens into it and converting them all into cro tokens.
It is not uncommon for them to run specials like 5% cash back or 50% off a limited amount of crypto, but these are temporary. It's worthwhile to have some extra cash to wait for one of these opertunities. My referral code is jwdsryp7mk