1. You could say: "What do you have?" or "What have you got?" If the type of measurement is implied, then you can say, "I have 20" or you could specify, "I have 4 feet, 6 inches" for clarity. It does not sound odd.
2. In the US, we tend to use "dreamed", and both versions would be fine, although the meaning could be slightly different. The use of "having" is fine.