The other question raised is right from the power's description itself (FRPG Page 26):
"While you are conscious and wielding either a light blade or a heavy blade, you MAINTAIN a field of magical force around you.
This fiels provides a +1 bonus to AC, or a +3 bonus if you are wielding a blade in one hand and have your other hand free (not carrying a shield, an off-hand weapon, a two-handed weapon, or anything else).
If you become unconscious, your Swordmage warding disappears. You restore it by taking a short rest or an extended rest."
This looks like if the warding is interrupted, that benefit goes away until you take a rest period (short or extended). So it matters not that changing from one to two and back are free actions, but the one hand warding is not MAINTAINED when you do so. So you are back at the +1 until you take a rest to re-establish your warding.