Welcome to AudioReview. Good snag on the ADS speakers. I miss my pair from years ago. The tweeter domes were treated with a coating that as you noted is sticky and of course collects dust. I would not try to clean them. You might remove the coating or as you mentioned damage the tweeter. They are fused but those are to protect the tweeters from too much power but a lot of tweeters are damaged by driving a low output amp or receiver into clipping distortion and the fuses will not protect them in that instance. I would not use treble boost with theses speakers. As I remember they had very nice balanced highs. I would listen to them without bass or treble boost for awhile as you get used to the sound of the speakers.

You should be able to order a new tweeter from Bose. I have seen tweeters that look like the ones used in the Bose 401's but I do not know if they would match up. As you may have noticed Bose is a name that has a few detractors here but I think they would be worth repairing. Of course I also think the ADS will give you a better glimpse into accurate sound reproduction.