Its ass backwards. Your upstream is on the high side, Your SNR is perfect, but your power level is high as well. Something is either wrong in your stuff coming to your house, which could be attributed to water in something or just maybe something else (funky upstream out of your tap outside). Because your downstream should be lower (dont get me wrong, modems will function at 12db just fine, but they are made to function between certain ranges and that's above and beyond and unnecessary). So something would definitely appear wrong, because that being so high and the upstream being so high usually indicates something.
You have any other services from Comcast? or just the HSI?
And those levels, although they are unbalanced -- your upstream is on the high side, but possibly bearing merit. But the downstream is high, for anything I would say.
Where are you located? As well?
(By the way, this is all assumed based on what you've given me, so don't go flying off the handle on any employees or anything or saying "I know someone from Comcast and they told me this and that" because that shit -- is annoying. So as long as we keep this kosher, I can help as much as possible.)
And as repetitive as it may seem, you may want to check and make sure are your connections are tightened down (not hulk style), because even finger tightened will do you a lot better than slightly loose. By connections, I mean: at your modem, any splitters in your house, any splitters on the outside of your house, and your 'ground block' to where your incoming line first meets (if you have one).
Forgive the ridiculous long post, I just like typing.