I increased KDF from 100k to 600k and then did another big jump. I had never heard of increasing only in increments of 50k until this thread. If that was so important then it should pop up a warning dialog box when you are making a change. That seems like old advice when retail computers and old phones couldn’t handle high KDF.
Do you still have your LastPass export? I can see you have changed your passwords. But, if you have the export, that’s 80% of your recovery. The final, laborious 20% will be resetting your passwords yet again. But, that’s better than starting from scratch.
Signing in from a different device like your gaming computer will be important to rule out hardware issues like keyboards, and then software issues browsers, extensions, etc.
Glad you have written down your master password to reference. I used a complex password for years and then one day it stopped working. I eventually figured out I had forgotten a small portion of it. Odd.
Hope you get back in and trust the first thing you will do is an export of your vault once you’re back up and running.
Good luck!