Definitely sounds like an account problem. One option is to back up all your personal files, then do a clean install, erasing the disk drive at same time. Then after setting back up copying your personal files back. Time machine is good at doing that. However I would not recommend backing up library because it may have corrupt java or other files.

Another option is you migrate your personal files across to the Test account & use that account instead. That is of course if you do not suffer the same issues with Java.

If you do not do one of those things, you will continue to have the same problems. It's best to bite the bullet & reinstall the system or if the 2nd account is ok then to move across to that one instead.

When doing updates after installation if that's your choice, choose the offline stand alone combo installer. It's the safest & has all the updates in one installer file. They are usually very large files however.