[raverbashing]

"In my experience, folks who pay A WHOLE NINETY NINE CENTS OF MY MONEY have very shockingly high expectations of polish / quality / feature selection (but no desire to e.g. read what the software actually does)"

What you do? You shut them out.

Not "remote disable them". But feature/support requests policy has to be simple. Either a user forum, FAQ, etc

You should absolutely not waste your precious time with this kind of work. If they want a refund just give it to them (not sure how easy this is on App Store or others)

Also, if this is so overwhelming, raise the price If they really want this so much they can pay 1.99

You don't need to ignore everything they say, but take it with a huge grain of salt.