Nice Job.
The thing that saved you is there was already a concentric hole in the fitting to guide your drills. I just got done removing a broken bolt and because of the location, there was no way I could get the drill exactly centered. I did wander into the threads a bit, but it finally came loose (using a little heat and vice grips to turn the stub on the back side.) There were still enough threads that a new bolt could grab on to. Saved me from having to buy ANOTHER helicoil kit (of course I didn't have the size needed.)
Perseverance pays off.
