I am on 17 of 29 trays and my front top teeth are now slanting outwards in a way I hate. Should Invisalign do this?

A good professional Orthodontist should not get angry or upset. He should explain and show you the process step by step and make sure you would be happy with the end result. Sometimes in the middle of treatment teeth will be flared temporarily in order to make space for the other teeth to move. You should and can not put the aligners backward to reverse the result.  

Quite often teeth have to be flared temporarily to allow others to move. At the end of treatment they are pushed back into their proper alignment.   In terms of reversing the order, you will not be able to do that, your trays will not fit

First of all, no dentist should get angry at a patient for asking a question about treatment. You should be able to sit down with your orthodontist or a staff member and review your clincheck right thru your 29th aligner so that you can visualize the final results. Quite often teeth have to be flared temporarily to allow others to move. No, it is not a good idea to wear the aligners in reverse order to reverse the treatment.