Not an expert in barbs but ill try to answer your points :
1- Yes. Deadly Strike. Chance to block. %fbr. Woot woot.
2 - Ohm runes and Quiet crafts if youre really hurting for Vit. Also Runemaster gives you defense % per rune socketed , not life.
3 - You will still need max block if you want to farm dunc etc, as well as as much %DR you can get til you hit cap, and that you can achieve through lucky'd 1/2%DR runeword bases on runewords that already give you %DR (Vith belt, Nih Armor) and through TA trophy = 5%DR. Rest of the points go to strength because damage scaling.
4 - Yes to Wolf stance for that sweet CB and pretty much everything else. Or go Kraken on crafted barb helm for more damage, whichever works best for you.
5 - Invictus is still top shield for us. Since we dump everything else on STR after getting max block and all that. Plus it makes you nice and tanky with 10%DR.