C6220 dropped connection

The power is a bit too low. I would have the ISP see if they can increase the power up into middle range. 

Your power levels aren't actually to low. They should be from -7.5dbmv to 7.5dbmv. You're in that range. So saying yours is to low, isn't accurate.

But that's just a general overview or power levels as you're modem only connects to 8 channels. there's a wide range of channels and there can be issues on other channels that aren't showing up that it might be switching around from. That's where the actual logs help. (and show you have issues with the t3 errors)

I'm suspecting this because your upstream to downstream power levels don't align. If the downstream is where yours is at, we'd expect your upstream to be higher than what it is. So there's something causing signal interference. 

Whether its a cheap rb6 cable, splitters, a signal attenuators, etc. There's something in line thats causing signal issues.

Start with removing any amplifiers, signal attenuators, or splitters from the coax.
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, bad/old/cheap connectors, or corroded connections. Replace them if you do.
If you can, simply connect the modem right where the coax comes into the home. This prevents wiring in the home from being the issue. And some ISP’s charge if the wiring issue is in the home. So this helps prevent this. If none of that helps, the ISP needs to check the line.