.. 1: Spec - Get Dark Archangel. It's a mana regen feature and also your best burst facilitator. Get it. No discussion.
2: Spec - Veiled Shadows - this is a personal preference thing, but considering you're running 4 piece Satin (I can wholeheartedly recommend going 4 piece mooncloth, or even 2p/2p for dual resilience bonus, the 4 piece Satin bonus blows) you'll need all the added mobility you can get, and shoter CD on fade == goodly.
3: Gear - well, yeah. 4 piece satin is borderline useless. At least compared to going 4 piece mooncloth. Hell, some of the satin pieces are even inferior to mooncloth, from a *shadow* itemization PoV.
4: Spec - I'd _suggest_ (again, up to playstyle and comp) dumping points from imp SW: P and imp MB into Veiled Shadows and Twin Disciplines. Bear in mind that yes, points in imp PW: S is nice, but considering the mana cost of it, it's a toss up if you will have the mana to throw PW: S out everytime it's on CD anyway.
5: Spec - Sin And Punishment...well. it *can* prove useful, and it's the only dispel 'protection' we have. It's unreliable, DRs with your Psychic Horror (and itself), but it's still something.
6: Gear - You might want to look into getting a PvP CC breaking trinket at some point