The permafrost will stop melting as Alaska continues to cool (over a decade) and Siberia levels off. It’s really only melting on momentum at the moment. Much of the methane is not in land-based permafrost but under the Arctic ocean and is protected by pressure and permanent cold just as it is in the Gulf of Mexico.
Yep. I'd wager that it is part of the planet's temperature regulation system. When ice caps form and sea level drops, so does the hydrostatic pressure where the Methane hydrates are, they boil off, and help trap solar energy, reversing the process (warming things back up).