Two-letter domain names, even for some extensions more obscure than .org, are typically very expensive. For examples of pricey two-letter .orgs, see ct.org and eb.org from this list; they sold for $22k and $28k, respectively.

(Also, if someone has held onto a two-letter domain name for many years, there's a good chance they've been approached by domain traders — who are numerous and proactive — and refused to sell even for a competitive price.)

I think generally no. Given the quality of search engines today I think having a short domain name doesn't provide much (I'm not sure that it ever did, given my own experience with them, although maybe I'm unusual and I could be swayed I'm sure by experimental results).