A few questions regarding unholy pvp

Hello everyone,
as the title suggests, I'd like to ask a few things.

1) Bis arena gear - regarding a human dk with Ahn'Kahar, Winding Sheet, Polar Bear, Apocalypse, Ashen Ring, hc DV and standard PvP pieces, what is the second trinket and ring of choice? More specifically - non-hc DV or Scale - and if Scale - wouldn't it be better to have Might of Blight than Skeleton Lord's Circle? I do understand ArP is not much of a stat for unholy dk (or anyone while at lower percentage for that case), but nor is expertise and given Mourne, neck, trinket and ring, ArP would reach around 30 % just from "free stats in what is bis anyway". Doesn't that, along with considerably better proc (As much as str is better stat than AP, 1472 AP vs 450 Str is simply too much of a difference even with all the str bonuses, and burst is what kills people anyway), outweight non-hc DV + Skeleton Lord's Circle which is what I mostly see on dks?

2) Bis universal dueling gear - regarding an orc dk this time, what is the optimal resil to go after? Is it better to balance PvP/PvE pieces and thus have considerably better str+resil ratio and around 1250 resil (with jewel), or to go with pvp pieces and more resil? I do understand it very much depends on the enemy, but there simply must be a better choice. Also, DC or Corroded Skeleton Key?

3) Unholy dk vs ret - Am I doing something wrong there, or should it really feel as if I was hitting a running brick wall if the ret decides so? He can simply put on a shield, run around los and wait for that perfect HoJ when I evetually run out of CDs and he gets those two or three lucky crits and thus either kills me or puts me so far behind that i wont recover.

And last but not least 4) Is there a macro that will use frag belt and then cobalt bombs until belt is off cd again? I simply hate unnecessary keybinds.

Thank You for Your answers.

I am wondering the answers for the first question too.

As far as trinkets go, DV normal will give you 900ap along with the passive ap = 1156 ap. But if you have both DV + DV Hc combined, plus the Endless Winter and Ravenous Dead strength increase and Rune of the fallen crusader 15% str increase, it all stacks up quite a lot. You also get extra parry cause of the str and don`t forget DV has passive AP on equip, with both equipped its 544 passive AP. There was something about pets as well, but I forgot these details already, sorry.
As for the rings, Ive always used wrathful to keep the resi up, since I dont like the itemization in both of those rings you mentioned. On neck I use Ahn Kahar hc + Garoshs rage/Varians Furor for cloak. Ring of rotting sinew is fairly decent also tbh.

As for duels, It depends on your playstyle. I personally like to keep Full wrath with the exception of neck, cloak and weapon (bryntroll) and keep my resi around 1200. I`ve noticed that with high resi, you can be more offensive with your CDs and spam Scourge Strike once in a while without getting low HP. But my playstyle is more of an outlasting one.