Hullo Rabbijo,
Welcome to the Using Mac OS X Tiger forum:
1: I assume you mean the size of your icons in Finder. If so select "Show View Options" in the "View" menu of Finder (or use Command / j as the shortcut) and you can adjust your icons to any size.
If you are referring to the icon size in an application toolbar, look for "customise toolbar" in its menus ("view" might be likeliest) and look for an option to "use small icons" or similar there.
2: If my guesses don't answer this question, I suggest you indicate which app you are using for your wordprocessing. However, it's very easy to accidentally type Command / - which reduces your font size, so the first thing to do might be to show your font panel with some text selected to see what font size you actually have in your document. Generally you'd find this under the Format Menu / Font options in most Mac WP apps.
The other possibility I can think of is that you may have set scaling to a smaller paper size under Paper Handling in the Print dialogue, or allowed for a sizeable margin under Margins in the print dialogue. I haven't tested the latter, but I frequently use the first for printing to A5 from an A4 template, and of course it does scale down the document font size.
Incidentally 12 pt TNR
would look rather small on A4 (or US letter) in single column. It's about right for A5 with reasonable document margins and a book text appearance.
Cheers.