Hey, sorry I didnt see this sooner! Your best bet is a deep shampoo/extractor for the seatas and the carpet. You may also look into this AC cleaning device,
1Z einszett Klima-Cleaner Air Conditioning Cleaner. You will want to accomplish all of this in the same day to remove everything at once. Problem is, some cars just have a "smell" and I know that some of the older civics do have a certain smell, but its not bad, your BF may just be confusing this smell with smoke?