That is complex to answer as the blast itself can kill, blast effects can kill, the thermal flash can kill, and the radiation can kill.
It depends upon how far you are from the bomb.
Yes the tsunami did trigger the nuclear blast because the water got into the nuclear reactor and buggered it up
no
it is a slow painful death
yes, thousands
The blast effects (which is all the question as worded asks about) would be the same as the blast effects of a weight of TNT identical to the nuclear bomb's yield (by definition). However a nuclear bomb has additional effects that the TNT doesn't, but as this question only asked about blast effects, I won't visit them.
Some of the effects on the human body from a nuclear explosion are death (from thermal energy/blast effects or super lethal radiation exposure), infertility and blood disorders.
Blast, always blast.
It is painful
Correct answer is blast effect
Is death painful buy antifreeze and how long does it take for someone to die from it and what amount
none
35km