First, you can ask by saying "Can you tell me...?" I am as tall as my mother. I am as tall as my mother is. I am as short as him I am as short as he is. I am as short as he. All are acceptable, but the ones on top are used more.

Here is a page dealing with comparisons of equality. It is kind of long, but really explains it well. Hope this is helpful for you. http://dictionary.cambridge.org/us/grammar/british-grammar/comparison-comparisons-of-equality-as-tall-as-his-father

Tough question. In both cases both sentences are fine, but to my native speaker ear I'd follow a different pattern for them I'd say, I am as tall as my mother, but, I am as tall as he is. In everyday speech, you will often hear, I am as tall as him, which isn't strictly correct.