Incredible.  A realistic insight to what it would have been like for her.  I don't think Petunia is evil but everything was too much for her and there was no help available - no return address indeed!  Vernon and Petunia didn't just decide to abuse their nephew, it happened slowly over time, little by little until they (particularly Petunia) didn't even realise it.  Of course she would have cared for him like Dudley when he was small, how could a one-year old have survived any other way? I don't like those fics which portray the Dursleys mistreating Harry right from the start and seriously abusing him.  
Anyway, long review cut short, I think this is great!

wow.  I like it.

As someone with nieces and nephews, I can see the temptation to just let him cry. And how the lack of sleep wears her down also makes sense. But still, the poor boy... Petunia, how could you?