After years of no problems, laptop keeps crashing repeatedly, and EtreCheck and DriveDx's apparently conflicting reports

Hello,

Essential background first.

I have been on Catalina final 10.15.7 on MB Air 2017 for a long time and have been using my laptop in exactly the same way – many apps open with several-to-many windows in some of the apps, as I work-work, personal-work, read, research, play, in an interleaving way.

I seldom had any problems.

(To head off advice, I should mention that: (a) I keep a good eye on ActivityMonitor's dock icon set to CPU history, and (b) I don't abuse my laptop – while I work, etc. on it, sports streams are on the iPad and Spotify is on the smartphone.)

In early October my SSD failed and I got a slightly-used one in good health. All went well without any change for about 50 days.

Then I got three system crashes in a single day – one panic, one hang/freeze, and then a restart. The crash report window didn't stick around (or got obscured by the automatically opening apps and windows – I tried to find it, to no avail) and I could not find anything in Console.(?) The only possibly relevant message I found, I snapshotted and am attaching.

Then my laptop restarted overnight when it was sleeping with the lid closed – when I opened it, it was on the login screen.

So that's four crashes in 24 hours. I just left it at the login screen. An hour or two later I thought I heard its fan – and it was! Touched the metal around [esc] and it was hot as ****! (Why?) So I shut it down.

By this time the battery was done for, having earlier been on the skids. CoconutBattery had showed the health at 70-something percent, quickly degrading into the 60s, then down to 47 percent.

I had to replace the battery anyway but it wasn't easy to find one though managed to get a slightly-used battery. The technician said that the crashes were surely due to the battery.

CoconutBattery shows the replacement battery's health at 87 percent.

Logged into my account at the shop and brought the laptop home. Left it with lid shut (had to go out again). When I opened it at night, it had restarted – showed the login screen. So the crashes have a cause other than the battery.

So then I logged into the first-created guest account (and am still logged into that without any crash for 24-plus hours). I am not using it remotely like I normally use my laptop (so yes, work, play, everything is suspended or offloaded to the iPad and smartphone).

Did some research and then got and ran Avast, EtreCheck, and DriveDx.  

No virus found. I've attached EtreCheck and DriveDx reports, and looking forward to your input.  

Re EtreCheck's recommendation, I am loth to allow anything to auto-update, having been bitten by it and not trusting Apple after the passing of Jobs, and the Lion fiasco (and all this craziness of auto-syncing everything, the O.S. and apps trying to second-guess you and essentially 'taking over,' etc.).  

The biggest point of confusion for me is that DriveDx says that my SSD is in very good health while EtreCheck, giving a 'Performance: Poor' grade, apparently says that the SSD is done for, as reads/writes are taking too long(?)

So all I can surmise is:–

1. Some app, daemon, or file in my user-account is infected and causes these crashes.

2. The SSD is not as good as DriveDx indicates and it is unable to deal with my heavy usage of the laptop (disk mediation, and VM swap-ins/swap-outs).

Would appreciate experts' feedback.

Thanks,

Kersie