Re: the stimulus affecting your refund this year, here's my guess. It does not affect this years taxes. It did not affect last years taxes. If you didn't qualify for the whole amount last year, or you missed the deadline, of you didn't get it for some other reason, you can get it this year instead.
When you are initially entering your info in a tax estimator, if you don't tell it that you already received your stimulus, the calculator says "oh, well, you can have it now" and adds it. If you then later put in that you *did* receive it, it takes it back out.
Just my guess...