Mac: Can’t use open/save dialogues or spot light properly. Apps often crash

I have a MacBookPro Mid-2015 model that is running 12.6.7 and can’t update past this. 

It has the following issues:

• When using the open or save as dialogue in all apps to browse my files, it says “loading” for around 10 minutes before it displays any files.
• Spotlight takes a good 20 minutes to return results.
•  Many apps will hang or crash at random.
• Saving a file via an app often causes the app to hang.

I think I will probably have to do a clean reinstallation. But I just want to see if I can narrow the cause so as not to recreate the issue after the clean installation.

Steps I have tried

1. Running in safe mode: All problems will go away, but return when safe mode is exited.
2. Setting up a dummy user account. The problems occur in the dummy account.
3. Booting into disk utility and running disk repair. 
4. Using Onyx to clean all caches and then waiting a week.
5. Using a terminal command to rebuild the spotlight index and waiting for a week, so it has time to rebuild.
6. Calling Apple Support. They checked the extension folders and start up items, but could not find anything.

Attached is a report using EtreCheck. I check it and cannot find any obvious cause.

However, EtreCheck will only run in safe mode. In regular mode, it just gets stuck on the “checking software” stage. 

The only thing that has changed recently is that I started using OneDrive. After the problem happened, I uninstalled OneDrive, but the issue remained. After a week, I reinstalled OneDrive, but it is still a problem. 

Could OneDrive be the cause?