"However - this raises what I believe to be a major problem - insensitive audiences who don't listen to what the singer is doing but instead, plough ahead with what THEY want to do."

I agree with what Jim said about choruses/refrains - it's one of my bugbears as well. I would actually distinguish between a 'chorus' and a 'refrain'. A chorus is something for the audience to join in with (if they must - yes, even the tiresome bellowers, dirge merchants and the pestilential harmonisers) but a refrain is an integral part of the poetry of a narrative song - a device to build tension, and sometimes, I feel, it's best if it's left to the singer.

By the way, if I think the bellowers, dirge merchants etc. in the audience are slowing me down I try to carry on regardless at my own pace, or even occasionally miss a beat at the end of a verse to really throw them off.