Compound sentences need commas.
Deleting the word of is the least disruptive way to correct the grammar here.
Sometimes you shouldn’t capitalize the first word after a colon, but there are times when it’s right to do so. One of those times is when the colon introduces more than one sentence, and another is when the colon introduces a direct question. Both of these apply in the example.
“It was nice to talk of normal things, but at the end of all the stories were the same questions: Would it still be there? Or would the event still happen?”
(The author of this example also offers writing advice to writers of “fictional novels.” *sigh* This is why we can’t have nice things…)