Drop it except you have real plans for it. As for sale, It will need a major miracle expecially if it means nothing. Been Domaining for 10+ years but I am by no means an expert
Yes definetly,no matter what is the extension of it. I have sold LLL.info for $1000 to private buyer last year. You should develop the domain and let it rise in PR then sell it when the price is meet your expectation.
If you have full form of your SHORT domain name, then your domain name have higher rates... Same with .ORGs
well choosing LLLL.net would be a better idea, at least if LLLL domains get more profitable than you'll have turn it in to cash earlier than a LLLL.org domain