2) there is a 277 tanking weapon in ICC, kisko:
http://www.wowhead.com/item=50708, it's just a bit underwhelming in comparison to even the ICC10 weapons.
3) currently, the stats on a weapon don't matter that much, as long as it is a slow one (with slow, i mean +/- 2.6). this is because fast tanking weapons have lower weapon damage, which means your seals and half your strikes do much less damage. i believe the best weapon currently is one of the wrathful weapons, since they got a lot of STAM, 2.6 speed, a blue socket for extra STAM and a decent amount of AP (264 wrathful has 129 AP, compared to 271 mithrios with 56 STR (117.5 AP when converted including kings); 277 wrathful has 149 AP compared to 284 mithrios with 134 AP, but has 1 less STAM).
4) in addition, there are currently some wrathful items that can be a pretty big upgrade, depending on where you start. i believe honor currently converts at a rate of 1 honor per kill, meaning 70 kills (or even 10-12 heroic bosses when you got WG) for a 270 shield with 181 STAM and 7.6K armor. if you don't mind losing some avoidance stats compared to a true tanking shield, it might be beneficial for you. for a bit over 900 honor, you can get 264 boots with 181 STAM and a socket.