Since you have a CFI maybe you can trade flight instructing for the TW signoff somewhere. I actually got mine for the asking from a retired Air Force guy who just wanted to help out. The 15 hours thing is nothing if you already have a TW signoff. You will have maybe 10 hours or so from getting the signoff, and then you can ride along for whatever it takes to get you to the insurance mins. You are not that far from ready.