The light flickering could be in reaction to Sam's appearance under someone else's power (my favorite is God - but even Castiel is an option - he could have raised a second Winchester from Perdition. Sam was shot in the heart by the Colt, so the body shouldn't have survived the departure of Lucifer without assistance.)
I don't know that Death would have any resurrection power - actually, scratch that. Logically It shouldn't, but Tessa the Reaper was able to heal all-but-dead-Dean in season 2, so logic doesn't really apply. Still, Death made Dean's concurrence a condition of getting the Ring. I don't see why He'd feel He owed Dean anything else. It's not like Death liked or respected Dean. Or Lucifer. Or God.
Also, re Sam's powers -- based on Ruby's statement, it's possible Sam has superpowers without Demon blood but with the exception of Samhain, he's never demonstrated it (granted, a pretty big exception.) Anyway, God put him through a quickie detox once. S/he could have done that again - so it isn't a given that resurrected Sam (if it is Sam) has readily accessible powers. Obviously there is a long string of assumptions here. But I don't see a supercharged Sam fitting into a storyline that doesn't involve Demons.
still not convinced
I don't know that Death would have any resurrection power - actually, scratch that. Logically It shouldn't, but Tessa the Reaper was able to heal all-but-dead-Dean in season 2, so logic doesn't really apply. Still, Death made Dean's concurrence a condition of getting the Ring. I don't see why He'd feel He owed Dean anything else. It's not like Death liked or respected Dean. Or Lucifer. Or God.
Also, re Sam's powers -- based on Ruby's statement, it's possible Sam has superpowers without Demon blood but with the exception of Samhain, he's never demonstrated it (granted, a pretty big exception.) Anyway, God put him through a quickie detox once. S/he could have done that again - so it isn't a given that resurrected Sam (if it is Sam) has readily accessible powers. Obviously there is a long string of assumptions here. But I don't see a supercharged Sam fitting into a storyline that doesn't involve Demons.