To answer your questions. At your point and level do not go out of your way to gem for hit or expertise. Focus on your EH.
Your spec is a lot different than mine and im blood, i do not use rune tap or mark of blood, for raiding you will need wotn (will of the necropolis).
Corpse explosion isnt really useful outside of naxx, keep it if you plan on doing naxx but at your current health pool being def capped and badge farming you should go straight into ulduar.
For your glyphs and raiding make sure you grab rune strike glyph to be replaced by your dnd glyph.
in terms of talents, personally, i'd take your points out of rune tap move them to wotn, the last point put into hysteria (good melee buff) and take the point from corpse explosion and move it to necrosis.
secondly and i cant stress the importance of this for threat.
#showtooltipmacro that to all your strikes, it, ps, hs, ds, etc. do not use deathcoil as part of your rotation.
/cast Blood Strike
/cast !Rune Strike
That should get you started in the right direction.