The screen in question is drawn by CvReligionScreen.py. This file seems to be missing in warlords and BTS, so the original one is used. Copy this one to your mod if it's not already present in Assets\Python\Screens
Code:
szLabel = gc.getReligionInfo(i).getDescription()
# if (self.iReligionSelected == i):
# szLabel = localText.changeTextColor(szLabel, gc.getInfoTypeForString("COLOR_YELLOW"))
screen.setText(szName, szArea, szLabel, CvUtil.FONT_CENTER_JUSTIFY, xLoop + self.X_RELIGION_AREA, self.Y_RELIGION_AREA + self.Y_RELIGION_NAME, 2*self.DZ, FontTypes.GAME_FONT, WidgetTypes.WIDGET_GENERAL, -1, -1)
xLoop += self.DX_RELIGION
That's the code in question.
I suppose you can alter the first line to specify the size if you like, like
Code:
szLabel = u"<font=2>" + gc.getReligionInfo(i).getDescription() + u"</font>"
It's a bit trial and error to see which size fits best. Obviously the screen can be altered to make more space for each religion, but that requires more programming knowledge. Make sure you don't alter the leading tabs/spaces. Python doesn't like that.