I rarely visit before finishing the puzzle unless I'm stuck on the endgame, here I'm not even that far. I think the 'incorrect replacements' is a clumsy way of saying use the letter in the clue definition that is changed, not the replacement letter. That way at least my first few incorrect replacements at least appear to be spelling something as the replacements do not.
What I do take issue with here is that some of the clues are dire, with definitions that are frankly tenuous at best (7dn for example), and one (14ac) which I still can't fathom even given a limited number of possible replacement letters!
I rather think this will end up on the 'life is too short' pile. It is a very short pile. Good luck all.