Question about Dex's mom

It wasn't the exact day Dex went to visit her, but her final scene (where the shot stayed on her at the end) was suggesting the end was nigh. From that we take it she would have passed by the time the next year's day comes round.

For his sake it better not have been that day, otherwise he'd be forever remembering the anniversary of his wife and mother's death on the same day each year!

No, she did not die that day. He was crying and upset because she was so sick and close to death, and because of the fight he had with his dad. He didn't deal with her illness very well.