As we are born with a "free will" we have no restrictions which roads we want to travel on. In our 6000 years of civilisation we have travelled (to generalize) the way of "get instead of give", with the outcome we all can observe. We stand on the brink of extinction through breaking the chain of nature and pollution of the planet alone, never mind the possibility of extinction through nuclear weapons.

We don't know much about all there is to be known about human life. An armageddon of western civilization does not equate neccessarily with humanity's extinction. Nuclear winter could indeed be harsh times, but life as successfully harder times. Pollution is at a global warning level, some places show signs of minor breakings in the chain of nature but although I can conceive of critical breakings from unrestrained destructive human fury, I don't think that we humans have reach enough of objective reality knowledges to be a fatal threat to our specie yet. 

My questions are " Why would a Creator create beings so inferior and destructive when he could have made "robots" to do jobs for him ?"

The whole Universe is imperfect, inferior and destructive. We are made from it, so there is no way better robots could have been made to do the jobs in this Universe. We have to get on with it. Our body and mind won't ever reach the perfection that our spirit is longing for. Something like "the spirit is willing but the flesh is weak."

"What are the jobs that God wants us to do, once we are in his spiritual kingdom ? Are we to sing hymns all day ? "

Again, I don't think we can make any assumption on the spiritual kingdom based on earthly analogies. All I can suggest is "what would it be if everything was perfect and I didn't had to care for all the weaknesses of my body and all the stupidities of my mind?"

I think these are valid questions.

Other questions like "What happens to all those atheists that have ever lived and live? Is God going to throw them into a lake of fire ? Or those people that have never even heard of God ?

Again, this is confusion about what our mind knows and what our spirit knows. People that have never heard of God or Jesus do also long for a spiritual kingdom. They do also try to live in harmony with their neighbours. They do also have a sense of morality and are not more or less sinners than those that have heard of God through Jesus.

Yet is a criminal—murderer, or whatever, going to hold any job in God’s spiritual kingdom ? Does God set conditions for being in his kingdom and why ?

The only sin that won't be forgiven is the sin against the spirit, I don't know what it is and I hope you don't know either. What would happen is probably oblivion, because I suspect it has to do with playing with the capacity of a spirit to sustain eternal life.

Would God " immortalize " human beings with the risk of causing havoc in the heavens as well as the earth ?

We will be immortalize like "angels", no chance of havoc.