1. First conditionals can be backshifted. Second cannot, because that would give them the appearance of third conditionals, and change the sense.
John: "If you come late, I won't be there."
John said that, if I came late, he wouldn't be there.
John" If you came late, I wouldn't be there."
John said, that if I came late he wouldn't be there.
If we want to bring out the difference between the real and hypothetical meanings in the reported versions, we would have to use different words, as I explained in another thread.
2. In your example, you are possibly right. In practice, those people who use the 'were' form in the first and third persons in hypothetical conditions would be so used to doing it that they would use it in a reported first condition. Many people do not use the 'were' form anyway, so the question would not arise.
This is the sort of question that would have provoked fierce debate in the tracts of the Society for Pure English in the 1920s, but interests very few today. If you wish to use 'was', do so.
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