Shat happens. Broken bolts can be a pita! One time I tried drilling through a broken exhaust manifold bolt. I dulled a few drill bits and couldn't drill through it. Then one bit I tried cut through it like butter, right through the bolt and into a water jacket! Nothing a lot of thread sealant couldn't fix!
If you get that bolt out, tap the threads and you're good to go. I wouldn't worry about a tiny piece missing, it'll probably seal fine as long as the break isn't where the o-ring sits.
It's easier to criticize than help sometimes.
I'm not a genius in real life I just play one on the internet.