Have you tried moving his system closer? Have you tried using your system near his location? It’s not just microwaves that can interfere with wifi, but also some kinds of fluorescent lights, or even infrastructure (pipes, electrical, mesh retaining, etc).
What is the signal db loss? Ping is a catch-all metric but isn’t reliable for nailing down specific problems. Also the varying ping times is called jitter, and some jitter is perfectly normal - wifi tends to amplify ping and jitter. Don’t get too hung up on high ping unless it is a problem.
If db loss is acceptable, is his tcp/ip stack compromised? Run a virus check, ensure his network configurations aren’t being hijacked (check dns, proxy, etc). Reset the stack and configs if necessary.
Has his router been compromised? There is firmware that is going around hijacking routers for botnets - very hard to identify and reverse from what I recall. Try another router if you have one. Aside: Might be a good idea to factory reset the router and start with a clean slate too.
Is your wireless network congested? too many devices can cause large ping and jitter, even if they aren’t on your network. Removing devices, changing wifi channels, disabling guest connectivity, and enabling game mode on the router can improve the congestion issue to varying degrees.
TPM has nothing to do with networking, which is good because there are bootable USB OS’s you can run to test your hardware without wiping your current install if you feel like it might be another type of compatibility issue (TPM would make this much harder to do).
Is…is your soda not normally soggy and salty?