Unreliable/Unstable WIFI Connections due to RFI Interference

I have not had reliable Xfinity WIFI connections for the last 3-4 months.  Wifi devices (phones/Rokus/Rings/Fire Sticks, etc.) sometimes connect for a minute or two and then the connection gets dropped.  I am paying for a high speed (1000 Mbps) internet connection and routinely get 800-900 Mbps in Speed Tests from my ethernet-networked laptop. 

After many hours on the phone or chat with many online Xfinity techs, I have reset my system too many times to count as I always have to go through the prescribed trouble-shooting steps for each phone call/chat.  I have had at least 4 tech home visits and 3 modem replacements. No one can improve my connectivity issues. The last tech visit at least identified RFI interference around my home as probably a main cause of my dropped connections.  This tech did a location scan for RFI interference around my house/address using a small portable radio set on the 1700 AM band. Major interference/static was detected around my whole house and even out to the street.  Walking down my street showed only my address as having interference! Tech suggested that all of my uninterruptible power supplies could be a source of interference so I disconnected the three UPS units in my system. To more accurately determine sources of interference, I bought an EMF meter/RF spectrum power analyzer.

The RF analyzer indicated major emanations from my LG washing machine (which has a WIFI connection) so I unplugged the unit. That helped a bit but I still had dropped connections.  

My next step was to get a couple of Xfi Pods to set up an Xfinity mesh network.  That helped a bit more such that my Ring doorbell finally connected - but still sporadically.  Phones/Rokus still had the dropped connections.

I do not know what to do next.  Xfinity tech service is at a dead end and given up on me. 

AT&T is not an option because even though my neighborhood has fiber optics available, the POTL copper wires to my house is in such bad shape that they can only offer me 45 Mbps speed!

Anyone have any ideas on how to fix this situation?  I am desperate!

Thanks, FM3