The best answer to #2 is that he never knew Padme had twins, and was in fact led to believe that her child had died with her in childbirth. Why he couldn't "sense" Leia on Alderaan isn't clear - that ability seems to come along as needed by the plot. A better question may be: why didn't he know Luke was around? After all, he had the same last name and was hidden on Anakin's own home planet, in the very house his mother lived in during her final years. For #1, perhaps she was remembering her adopted mother, mistaking her for her real mother.