My EtreCheck report for my 27"iMac, late 2015 build. Original question posted Oct 24, 2022 11:40 AM

Before considering an erase / reinstall, start with the simple things first.

Create a brand new Time Machine backup, ideally one using a different external hard disk drive than the one you are using now. The reason for that is an abundance of caution: you never want to be without any backups at all, not even for a short period of time. That will also obviate any concerns regarding the questionable manipulation of files on the existing backup. Just set that one aside for the time being. When you eventually fix whatever's wrong, you can erase that Time Machine backup drive and start a new set. Time Machine will continue to back up to each one, cycling between them with each successive backup.

Then, restart your Mac in "Safe Mode": How to use safe mode on your Mac - Apple Support, and determine if the same problems occur while using your Mac in that mode. Specifically, the numerous app crashes that have been occurring should not occur. The Mac's performance should be more or less normal and it should not run slowly in Safe Mode.

Use it for a while in Safe Mode, perhaps an hour or two. Time Machine works normally in Safe Mode, so continue to let it back up.

Then, restart your Mac normally (not "Safe Mode") and observe again.

I suggest you rid your Mac of "Malwarebytes". It is not monopolizing that Mac's CPU to a great extent, and its memory usage is "only" 150 MB (about the same as Safari), but it's not something anyone needs to install and run continually. Besides, it's crashing along with other programs that should not crash, adding another complication to troubleshooting. Follow its uninstallation instructions. If you should inadvertently install malware it's easily removed without having to install it, or anything like it.

Other system add-ons and Internet plug-ins should be removed because they are old / outdated / unsupported / no longer useful or were never useful to begin with. They are described under Internet Plug-ins and 3rd Party Preference panels. I recommend you get rid of all of them with the possible exception of Paragon NTFS, which may be required if you have a need to read and write to PC-formatted external storage devices. Again please be sure to follow their respective uninstallation instructions.

Only after considering and exhausting each of these suggestions should you consider the "nuke and pave" approach. It remains as a last resort.

I agree with pretty much of what John Galt already suggested. I would start by evaluating apps & plugins that may be old, incompatible or not really necessary and remove them as appropriate; but I think that in the end you are headed toward a wipe & reinstall.

Here are some additional things I noticed in your Etrecheck report:

• You have only 8GB RAM. While Monterey will boot & run in 8GB, it's about the minimum necessary. I suggest increasing RAM to at least 16GB. Even moreso since you appear to be doing photo & video editing.
• You have a fusion drive. User experience with fusion drives under Catalina & later versions of macOS has been rather hit or miss. If you can afford to replace it with an internal SSD things will be much improved.
• You have a number of very old and probably incompatible things installed, including Silverlight, Shockwave, Realplayer ...
• You have quite a few HP, Epson & Canon printers/scanners installed; I suggest removing any that you are not now using.
• You have a number of apps that appear to maintain live internet connections: weather apps, parcel tracking, etc. These all consume system resources when running.