I see the parallelism here, but let's make it more explicit since you shouldn't use delete to deallocate memory allocated with new[]. Something like "An object allocated using new should be deallocated with delete. An object allocated using new[] should be deallocated with delete[]

I can't think of a way to make it flow well if we keep to 1 bullet point, hence, I split it into 2. I kept the phrasing of the first part of each bullet point, since it is in the Destructors are called when one of the following events occurs: part.

I took a whack at it.

The thing to do here is break this out of the code block, and add a section immediately after that starts:
Three ticks: ```output
A3 dtor
...

I've seen the pattern you are trying here in some of our docs. That's an old pattern and I remove it when I come across it, so don't want to introduce it afresh in new docs.

"```Output" with a capital "O" has over 1k matches, but "```output" with a lowercase "o" only have 60 something hits. Is any one of the above preferred, or it does not matter?

It doesn't matter because we are relying on the tag for the code block type to do the rendering for us.