1- I'd go for 'panel'. You could say the jury is made up of...
In BE we could say jury is\are. Our relaxed attitude towards singular and plural is different from many AE speakers.
2- If 'then' took the second position, it is not a comfortable place. It comes there because it is being modified by 'so'.
3 - I'm afraid not- we put the adjective before the article with this structure.
4- I'd spell it 'nay'. It's an old-fashioned negative that still crops up sometimes, often used for emphasis, as here imo.