First problem: you cannot use custom column lookup names in template.xhtml. See the "Customizing the Descriptions template and Section lists" section in the
Creating Catalogs: Start here thread.
Starting with calibre 2.1 you can use custom columns, or in fact any valid calibre template, in the templates defined in section_list_templates.py. These templates are used to generate the reference lines in the various contents sections.
Finally, you can place a custom column in the description section (extra description) and in the comments section (merge with comments). Although these are limited to a single custom column lookup name, you can add an arbitrary amount of information using columns built from other columns (a "composite" column). You can insert newlines into a composite column intended for use in a catalog using "<br>", as in "{#myinfo}<br>{#somedate}"