I keep meaning to do a flowchart (or web simulator for XP), once I have enough "curvaceous tuits"

If you can charge $15k to the FB credit card by its anniversary date (to be safe, I try to do it by statement closing the month before my anniversary date (so June in your case)), you'll get 60 XP to help you with requalification and rollover (and 1.5 FB miles per unbonused $ isn't actually giving that much up) . Then it's 7 F segments on Delta to keep Silver and you rollover the excess. With the late start, it might be a 2.5 or 3 year journey to Platinum.