Interesting but is the alignment out in two planes? Perhaps it is my autistic leanings but I would have liked to see the shot dead centred and perfectly square on - but very good, evenly focused and lit.
Hmmm.... That's weird. There is no reason the photo should go out of focus just because you straightened it. But, sure enough - the second photo is out of focus. As to editing your photo, don't you have an "Edit" button at the bottom right under the original posting? That's how you change photos, by clicking on that button. Second from the left - "Quote" "Edit" "Report" "Reply" Then in the window that pops up, click the button third down from the top - with a strange name: "1/3 Change". Then click the "Choose File" just like when you upload the original. That should do it.
I'm glad you weren't able to replace your original with the new one as i far prefer sharpness to the shot being absolutely straight.