I think it would be much more beneficial for you to ask for a local moderator. You have several very active members who, if they are ready to accept responsibility, should perhaps apply for local mod positions.
We are going to later ask for a moderator, but the need for other boards (especially other discussion which is meant for off-topic) is imminent. If there is a moderator moderating that board, he will not be able to delete many of the posts which some people see as spam, because many are not spam but belonging to off-topic board. Unless the moderator just want to be harsh. It is worth mentioning that moderators have fast response to the posts that I have been reporting on the board.
Yes, I agree with what you said. I happen to be normally active on the Nigerian local board, and I also suggest that there should be some sub-boards, and after the sub-boards, a moderator should arise. The reason is not far from what you have said; there are most topics that should just be on the off-topic board, but they all just get jam packed on one single board, and if there are any moderators now, I think it's actually going to be a very stressful or confused duty for the moderator, but if there are sub-bards, then it will be easier.