Q2.
The following is pretty obvious so maybe I have misunderstood your problem, apologies if so.
All I do in such circumstances is in the Editor highlight a <blockquote> that has no text after it with the mouse and move the mouse curser to the start of the next line (so, for example, in your file select <blockquote> on line 11 and carry the selection to the first column on line 12). Right click>Copy that with the mouse and paste it into the Find box, and have the Replace box empty.
Do a Normal mode Replace all and all the {unwanted} <blockquotes> without any text after them disappear.
Then do a "Beautify" and all the </blockquotes> will disappear.