(1) IIRC, MalwareBytes could be installed without having it take over Real-Time Protection. That way, it would not turn off Windows Defender, & it could be run occasionally On-Demand. That should be fine. But it's good anyway to fully uninstall it a while during this episode just in case
(2) That's right about System Settings Broker. Sometimes an app will crash as a one-off or few & far between. I've seen it with Edge & with File Explorer. That's ignorable.
(3) WSReset works for me (but I have no problem to begin with). It blinks a bit at a Command Prompt, then the MS Store opens & works well. Too bad DISM & SFC - & even an In-Place install - did not restore its functionality for you. That's a sin - those heavy-hitters are designed to put Windows back in shape. Very sad.
"wsreset says: The specified device, path, or file could not be accessed. Maybe access permissions are missing for these items."
Permissions does sound like a good possibility. But battling them can be difficult & dangerous.
(4) I can see why you don't want to do a clean install with so large a list of installed apps including 3 that are top secret. I think probably a bunch of the Dell apps can go. Support Assist is duplicative - Windows does all it did except fetching driver updates from my Dell site (it never got them all - I had to go personally get some) & alerting of BIOS updates. I uninstalled mine (& a bunch more of Dell) when my Dell Inspiron 3542 warranty expired. And your site doesn't even have Win 10 drivers. I don't know why you've got 3 apps calling themselves Support Assist. Do you ever use it?
I never had Dell ControlVault Host Components Installer. I don't even know whether uninstalling it also uninstalls the components themselves. It sounds like a powerful thing that may have a connection with hardware & could possibly cause file access problems. Have you looked through its settings, if any? Do you ever use it? I think possibly Windows does a lot of that too. It could be duplicative.
Dell ControlVault Host Components Installer 64 bit
Note: That is a 3rd-party site. It sounds informative, but I know nothing of downloads or links that are there.
I also never had Dell System Manager. It is bigger, but doesn't sound as possibly ominous as ControlVault. But I'll be damned if I can understand what it is from...
https://www.shouldiremoveit.com/Dell-System-Manager-16059-program.aspx
Dell System Manager