@trolltoll Just some quick points I’ll throw out that are really rough/crudely written to get the ideas across more than the actual finalized language:
Your audience doesn’t care about YOUR desire to fill the role, it’s about filling THEIR needs. So the intro should be more along the lines of: “I’m applying because my education, experience and passion for social justice make me an excellent choice for the position of Editor.” Anticipate their needs (nonprofits are always looking for funding): “As a nonprofit in a difficult economy, I understand how crucial fundraising is to fulfilling your mission of championing social justice via research, education, training (etc.) (It should be public record so look into where most of their funding comes from, and mention it, e.g. Corporate funding, or grants, private philanthropy, etc. You need to know where they’re coming from to write an effective letter)... Having written material that clearly articulates your message, tone and house style is vital for reaching professional donors, receiving grants, and effectively communicating the results of NCCD’s research, etc.
Next you’d want to show why YOU’RE the one they need. How your previous experience translating technical Physics papers into digestible material, as well as your 18 months of regular daily publication totaling over x words published, demonstrates that you have the talent to do the job as well as the tenacity and drive to consistently deliver large volumes of exceptional quality writing. Combine this with your personal passion for their mission of making the world a just and fair place (example needed), and you’re well on your way to demonstrating why they’d be crazy not to interview you.
As far as the salary itself. I’d give an actual number, and explain how you arrived at it: E.g.
I reviewed salary data from salary.com and the median salary for editors with my education and experience in the zip code of…. is $x. Because NCCD is a nonprofit and I understand there are budget constraints a 20% discount from the median seems like an appropriate adjustment. The result after this adjustment is $y, but is open to further negotiation.
Anyways, I know this was really unpolished, but hopefully it gives you some crude suggestions for addressing the underlying concerns your audience may have.