Adjustable door threshold bottomed out and grouted in place
So this is what happened. First I bought a handheld grout scraper, but it was way too wide; I wanted a thin cut if possible. Then I bought and used a 1/16&quot; wide mason cutting wheel on my cheap harbor freight 4&quot; angle grinder, you can see results in pics. It did the job, but the grout crumbled and collapsed. Finally, I used an old flathead screwdriver and hammer to chip grout from screws until I could raise the threshold.
Lessons Learned:

Good: Goal was to raise the threshold and stop bug traffic. Goal accomplished.
Bad: I should have started inside kitchen rather than outside in garage. I think I could have kept a straighter line and not damaged the threshold so much. I didn't realize the threshold damage until I moved inside.
Bad: I should have tried using a Dremel cutting wheel cutting wheel first. The wheel width would only been 1/64&quot; thinner, and maybe the grout would still have collapsed, but I would have had better control with a Dremmel than the heavy angle grinder. Also in hindsight probably wiser to start with smallest cutting tool and move up if the situation allows.
Bad: I ended up trashing the threshold.
Good &amp; Bad: My mistakes in this project force me to learn how to remove and reinstall a wood threshold and grouting. Acquiring new skills is never bad, but now I have to pay extra money and have two more chores to finish it.