I suggest that you get in touch with your ANC Commissioner to ask these questions – they’ll know the answer to the question (or at least how to find out), and it is helpful for them to know that residents are concerned. Otherwise they think no one cares. You can also call ABRA as this should be publicly available information. The information might be posted on placards outisde the establishment until the outdoor seating is approved.
I’m not sure if there is a law governing the outdoor hours, but neighborhood residents can work together with the ANC and the restaurant owners and introduce neighborhood preferences. In Adams morgan, I think they’ve been able to limit it to either 10 or 11pm. On U Street, residents in some buildings have been able to introduce into a restaurant’s Voluntary Agreement that outdoor seating areas be shut down at 10pm, in the hopes of setting a neighborhood standard.