User blog comment:Miskos3/Fairy Tail Episode 249: Tartaros arc: The Celestial King vs. The Underworld King, Review/@comment-25334245-20150909234624/@comment-7418318-20150910155630

For the first, just divide the chapter-number by 2 for a rough estimate.

For the second, no idea, but I can't wait for it to come out (or be announced at least).