WordPress MU nginx sub-site configuration

Hi all,
I’m having a problem with WordPress MU (using subdirectories) on nginx. I’ve set up the WordPress config as per the Codex instructions. My nginx conf is from rtCamp’s template.

The main/root wordpress site works perfectly. There are two problems in sub-sites/networks:

1. The theme files on all sub-sites aren’t found. Instead of using the theme at the root (files at https://example.org/wordpress/wp-includes/…, they try to use the theme at the sub-site network https://example.org/wordpress/subsite1/wp-includes/…)
2. Accessing wp-admin on the root site works great. But trying wp-admin on the sub-sites creates a redirect loop error.

I know this is a pretty complicated problem, but I greatly appreciate any help in advance. Thanks!