Hi there! He should be able to stay and work once he gets his OWP. From what I see here in the forum, there are already October applicants getting their OWP so your husband's should come shortly as well. So its really up to you if you'd like to extend it or not. Not quite sure how long it takes but I think I read before that its approximately 30 days to process.
If however, he would like to travel outside of the country in the future, he should have a valid visitor's visa AND work permit to be able to re-enter Canada. That's the only time that he would need to have a valid travel visa.