4. This means God can't run the universe anymore.
Death is not "ceasing to exist," but a change in ontos (mode of being), and spiritual death is relationally experiencing the negative aspects of God. God experiencing a negative relation to himself does not entail the loss of his attributes.
5. Physical death is the only price of sin.
This is just not Biblical. Else everyone pays their debt upon death. There is a second death.
6. But Jesus was a sinless person so he could physically die for us.
God did not tell Adam, "in the day you eat of it, you will die if you are sinless." The wages of sin is death, so sinlessness prohibits dying.