I have always had vision problems, but it has only been recently that it has started to impair my ability to operate a desktop computer. Mainly, I have become unable to read standard and small text, dark text on a light background, and viewing multiple images on the same page or in quick succession is difficult.

Could some of my fellow Linux users help me with the following?:

Setting a large-size font as the default for both Terminal and GUI programs. I already have IceWeasel, Medit, and LXterminal displaying their content in large print, nearly everything else has unreadably small text.

Configuring GTK and Qt themes via editing text files to make everything white text on a black background. Using the GUI config tools hurts my eyes.

Any Firefox extensions that provide greater flexibility than the "Display Images" option in the Firefox perseverances. Something that hides all images by default and allows me to show/hide images with a simple mouse click would be nice. In general, any extension that makes it easier to configure how websites display would be useful.

A good screen reader so I can still use my computer when my eyes get to tired for reading?

For the record, I am currently running a dual-boot of Debian Testing and Ubuntu Server 12.04 running LXDE on both.