FBReader does support italic. However DroidSans font (used in FBReader by default) does not include italic variant on some devices. Try to change font family in FBReader settings.

Yes. Put your *.ttf and/or *.otf files into Fonts directory on the memory card. New fonts will be available in Text section of FBReader settings dialog.

You also can set up your own directories for fonts, in “Directories” section of the settings dialog.