SUCCESS! removing the sprocket, that is. It turns out that this was one of those situations where "use a bigger hammer" (well, more of the small hammer) was the answer. This time I did everything I did before, just more of it. More force on the cheapo puller, more heat and more hammering and it finally let go. I am showing a picture of the lousy puller so that I can be rightly derided for the evils of going cheap. (But would I have wanted to grind down a good puller. I'm thinking, no.) Thanks for all the advice, the general direction of which was "go at it harder". No rocket science here (or even automotive science, for that matter).
John, your post seems spot on for where I am right now. The timing cover came off but the idler still won't come out and moves as you've described. Now I can just do what you did and things should be good. I'm just starting work on the A7, so a belt drive is probably in the future, but might be a deferred expense, since chain drives also work, though, I do love the way the belt in my A10 makes less noise and more juice.
Thanks again, guys.
Richard L.