Locations for applying for S1?

Hi there! My husband and I just moved to Shanghai a few months ago, and are planning to stay here for another year or two. I have a Z work visa with a residence permit now, and he is on a multiple-entry tourist L that requires to run every 60 days. His L does not expire for another 8 months (he got a year-long one). We couldn't get the S1 right away since I didn't have my residence permit before we left, but we were hoping that he might be able to get one now so we don't have to worry about his L anymore. I have two questions: A. Can he switch to an S1 even though his L visa is still valid for more months? Or will he need to wait until his is closer to expiration? and B. Would he have to return to our home country (USA) to apply for the S1, or could he get it in Hong Kong or Thailand (or any other Asian country)? (We brought a copy of our marriage certificate here, just in case!) Thank you!