Low Upstream Power - inconsistent speeds

I have been having massive issues with consistent speed.  I have an Arris SB8200 modem that is paired with the Google Wifi.  

The other day I was having god awful signal on my YouTubeTV service and i ran a speed test.  29mbps.  thinking that the issue may be related to the other 2 pucks in the house, I disconnected them and utilized only the main puck hardwired to the modem.  39mbps.  I pay for the gig speed.  

I contact Google because I'm immediately thinking, maybe there's a setting that's not set right.  Everything is good.  We call Xfinity, who has me check the modem by plugging the laptop into it.  Speed wise is good.  Moving on with life, reboot the wifi system and speed is 545mbps, which google says is not accurate, should be 80-85% of the speed from the modem since it's hardwired.  Literally 2 minutes later, it's 21 mbps.  Back to the modem and i'm in the 185 mbps range.  

Last night the house was empty and tested again, consistently in the 180-200 mbps range from the modem.  Contact Arris this time, and they say your upstream power is 41-42, recommend 45-51.  You also have too big of a variable in the downstream power ranging from 39-44.  Contact Xfinity to get them to release more power to the modem.  I did that and got told everything is functioning properly, and that's that.  Contact Arris and they said the inconsistent speed and signal is due to the modem not receiving enough power.  They contact xfinity and get told the same thing, nothing is wrong.

I will say  when I got this modem, it took 8 hours to get it configured right, as I had to make 4 calls to xfinity to find someone to set it up properly on the back end.  

What am I supposed to do here?  I am having massive inconsistent internet speed that is affecting both work life and relaxing life while watching TV.