No credit card required
Browse credit cards from a variety of issuers to see if there's a better card for you.
The Cash Magnet is not very useful if you already have the Freedom Unlimited, and the Amex Green is not very useful if you have the CSP. If you want to maximize rewards, try to fill out your 5/24 with other Chase cards before you move on.
And also, unless you're paying 0% interest on that 19% utilization, I'd pay those off before apping for new cards.
Slate is indeed a good option. Once you're done paying your balance off, you can transfer all or part of the Slate credit line to Freedom Unlimited or Sapphire Preferred. Win/Win!