grammar - conditionals: what's the difference between these two sentences?

There is a sentence in a paragraph from the novel 'And the Mountains Echoed':

"But these were gestures, Abdullah knew, acts of duty, drawn from a
well far shallower than the one she reached into for Iqbal. If one
night their house caught fire, Abdullah knew without doubt which

child Parwana would grab rushing out."

The scenario is described in the past tense.

But I learned that for conditional unreal things happened in the past, we can use the past perfect tense. So can I change the sentence to:

If one night their house had caught fire, Abdullah knew without
doubt which child Parwana would have grabbed rushing out.

1. Can I assume that the first sentence using the simple past tense refers to a conditional situation in the past (we don't know it happened or not) yet the second sentence using the past perfect tense refers to not only a conditional situation in the past but also something that didn't happen in the past?




2. If the paragraph used the present tense like:
   But these are gestures, Abdullah knows, acts of duty, draw from a well far shallower than the one she reaches into for Iqbal. If one night their house * caught * fire, Abdullah knows without doubt which child Parwana would grab rushing out.

In this case, could I assume that the "If sentence" describes something that happens now even if the simple past tense is used?