That looks like an SNR fault (the RxMER is very low, which is the give-away), which can happen without there being anything wrong with your setup. I get SNR fault's now and again, but normally my power levels and SNR are totally fine. So this shouldn't be happening all the time.
If high upstream power was the only problem you have then I would have said you need something like an Active Return Amplifier:
https://www.youtube.com/watch?v=kxarSx0rQ9M
You may need a coax re-pull if the cable from outside your property to the cabinet is not good enough.
Your RxMER should be above 34.5 dB for a decent quality signal. The Hub 3 is doing a good job holding on at 33 dB.
Attenuators won't fix your upstream. Most attenuators are for correcting the downstream.
Your upstream level could be improved by changing the tap at the cabinet, but I'm not sure that's going to help. It won't change the downstream SNR and your upstream SNR could be low too.
Btw, your modem would support a higher downstream power up to +10 dBmV totally fine. Usually the downstream and upstream are related and work in opposite directions. However with your problems who knows. The upstream power is high because the CMTS can't hear the modem, so the modem is increasing power to be heard.
The upstream power limit for two 64 QAM channels is 54 dBmV. So those channels should work until the power maxes out. Ideally you want the upstream power in the 35-49 range, as they may drift a bit and you want a bit of leeway.
If the current tech's haven't solved it, the principal tech should be called.
Hope that helps.
You may get better advice from one of the cable tech's on here.