1. Read the RMXP Help File for RPG::Armor. You'll find what you need there. For elements, basically returns an array of ints from 1 to 6 where A is 1 and F is 6. For states, I think it's just an array of booleans.
2. Assuming your elements follow the RMXP default values (200, 150, 100, 50, 0, -100), you just draw_text whatever value needs to be drawn. If int is 3, then write 100, etc.
For states, just check if the value is true. Then do whatever you want to add, be it draw an icon or draw text saying it resists that state.
3. You're going to be using a loop to iterate through each element in your database. If you have an array of element IDs to ignore, just put something like
next if DUMMY_ELEMENTS.include?(element_id)
in your loop.