It is not my opinion, it is standard Buddhism. Nirvana is not non-existence. The Buddha attained nirvana at age 35; he died age 80. For 45 years he was living in the world while at the same time in nirvana.Your version of morality says that people should seek not to exist. I hardly think that your opinion is very authoritative.
So, we have a two-part God. One part is immutable and does not change while the other part is mutable and does change. You cannot have one thing that is both mutable and immutable, you must have at least two parts.That means that his divine attributes do not change. Perfection rules out improvement. Any change by definition would be a degeneration, which also would be completely at odds with the concept of the God of the Bible.
Yes it does.Immutability has no implication on God's power.
MOSES: Lord, please part this sea so your people may cross to safety.
GOD: I'm sorry Moses. I did not part the sea yesterday and so I cannot part it today because I am immutable. Better swim.
An immutable God can never take any new actions, since that would be a change. Only the mutable part of a two-part God is able to do anything new.
Which is why an unchanging or immutable entity (or part entity) can never change what it does or ever do anything new. It would be a similar logical contradiction.God can't be irrational, because God is the very definition of rationality. God's divine attributes do not contradict one another.