That's quite the post, new guy! Let's see if we can get you settled into the driver seat! Also, if anything in this post is a bit off, I apologize. After all, I'm a frost tank.
Get the Arcane Shielded Helm from H Nexus (Grand Magus Telestra) or a Tempered Titansteel hat. Gem the helm with Austere Earthsiege (Meta) and Solid something blue for stam. For trinkets, run regular toc until The Black Heart drops. Need roll IMMEDIATELY, then head to H Azjol'Nerub for Essence of Gossamer (Hadronox). As was mentioned, rep grind with Argent Crusade until you can get the Arcanum of the Stalwart helm enchant. BANG! 540 def skill and another 2500 HP. Just make sure you're chasing tank gear. Regular ToC drops some phenominal tank stuff, not just the trinket.
I'll just link you one I think might be decent. Saves a lot of words lol
Talent Calculator - World of Warcraft
Note: I added Hysteria in there so that if one of your melee DPS is lacking OR you're losing aggro, you can kinda jump it up a bit.
IT, PS, Pest, DnD
DS x2, HS x2
Pest, BB x2, HS x3
For bosses -
IT, PS, HS x2, DS
Pest, DS x2, HS
repeat step two until you're looting.
Use cooldowns and dump as needed. Always use IBF ASAP on trash, and make sure you mark on trash and stick to the marks, otherwise you're bound to lose aggro from my experience with blood tanking.
...Thoughts of a philosophical Death Knight...
If death is the inevitable end of life, is life the inevitable end of undeath?