So, do Jehovah's witnesses believe there are two kinds of death?
This, I don't know. I don't remember focusing on spiritual death in my bible study. I came to that understanding after personal study, patient reflection and prayer.
What about who got payment for our sins?
I think you are a little biased in what you expect from an answer :)
<<<As in "here, the nasty creatures I myself created, in full knowledge that they would sin, did indeed sin by eating from a tree I myself created and made it a point to have grow near where my creatures would live, in full knowledge that they would eat from it, so here's the atonement/grace/ransom/whatever so they will be free". Who is at the receiving end?>>>
Man separated himself from God by sinning. God sent his son to teach and to reconcile man to Himself, forgetting man's sins and granting forgiveness and grace through Jesus. Jesus might have earned it for us by obeying his Father, but we didn't do anything to earn it for ourselves. Which makes it a gift that we can either choose to accept or ignore.
All of Romans 5 speaks about this as a gift/ not as something we have paid God for.
Tammy