1) I had assumed that if two characters were in the same charged situation, they couldn't Read a Sitch separately, so one had to help the other. Is this right?
Two characters can read the same charged situation separately. Their questions can get different answers, based on their playbook, moves, and relationships they have with the situation in question. If the characters want to do their moves separate, then they are able to do so.
If the one character wants to help one another character read a charged situation, they can, but they do have to explain how they are helping. Unfortunately, the helping character does not get to ask the questions, and does not get the +1 forward when acting on the information.
The helping option is a good one to those characters that have high Hx but low Sharp. Alternatively, those with low Hx and high Sharp are more likely to read charged situations separately.