I had this problem at the end of September, and the problem was my (eight-year-old) ONT was going bad. For me, the pixelation started at the lowest channels (e.g., 4, 5, 9, etc.) and got to the point that they were unwatchable. The HD versions of those channels (e.g., 504, 505) we much better, but had minor pixelation. It seemed like the "pixelation rot" was working it's way up.
I downloaded and used Verizon's in-home agent, which walked me through some troubleshooting steps (some of which you already tried). I don't usually have much luck with these tools, but the agent eventually concluded that this couldn't be fixed remotely and took me to an only trouble ticking system. I had a "new" (i.e., refurbished) ONT a few days later. The Verizon tech had a analyzer that he hooked up to the video out from the old ONT and showed it was bad on almost all channels. He swapped it out for a new one.