'Need to Know' is the perfect addon for 2 of your questions.
As far as Reck while in Creche proc, I see no reason to avoid doing so, the only thing I can think of is spreading out your +crit bonuses for more up-time on Deep Wounds / Enrage.
Creche vs BLF is a simple matter of adds.
Morchok has no adds, use Creche.
Yor'sahj has adds, use BLF.
Zon'ozz, the adds are spread out enough that Creche is probably better, UNLESS you're in charge of cleaving the boss and the Claw, in which case you should use BLF.
Hagara is hard to say... If we're talking 25 man, BLF is probably worth it. On 10 however, the tombs die insanely fast these days, so Creche is probably better.
Ultraxion is Creche.
Gunship, BLF.
Spine is obviously Rotting Skull.
Madness is BLF for Spellweave cleaving on Bloods.