As for runewords, you need to watch out to not lose too much defense, because runewords use only 1 rune vs uniques/crafts/sets having every socket filled.
From these runewords shaad axe is definitely worth looking at, but it has more synergy with non runemaster build, as you still get some defense per rune from it, which is very unique mod. It has more value for clearing, as proc of it is aoe rather than single targed. Another good one is nero, path of flames is strong even as non caster build, free fortress procs synergize with our skill tree too.
But these won't be massive upgrades. As I said before, warewolf set chest + belt combo is good. You will need to socket lot of sha runes with it to achieve 7 frames breakpoint.
Ad %ED yes, cap is 200%, only way to exceed it is through sockets, or if you are making a runeword, you MO ed before putting rune, and then runeword ed adds on top and can go over a cap (But as I said before, this is counterintuitive with runemaster, because we are losing runes).