Richard,
I think your questions are spawned from Christian oversimplification of concept of God and the reality, which includes the oversimplification of nature.
Biblically, God takes responsibility for death and the condition of this world as a spiritual lesson. Perhaps you may see it as "evil" on His part, but on other hand I think it would be likewise "tyrannical" to sustain the condition of human ignorance of evil. It would be akin Christian parents shielding their kids from concept of sex, because there's pornography and prostitution.
Why would God place the "forbidden tree"? Was it merely a test? I hardly think so, especially when you bring in the concept of foreknowledge into the picture, then the whole idea of a "test" dissipates. You could say that the humanity has chosen death in exchange for knowledge. I think that it goes beyond the literal picture of "eating the forbidden fruit", but also as an archetypal picture for freedom of choice. Ideally people should be able to choose death if they desire so, and even though it may be preposterous to believe that anyone would choose death over life... but we see this happens on daily bases... and it goes beyond our biological inability to re-generate.
I think that we oversimplify the concept of evil, because first of all it's highly relative .. just like our concept of "good". Evil always exists even in light of perfection. You can't have a reality without opposites. There's always pain because without pain our hands and feet would be pieces of badly bruised meat. Pain serves a practical purpose, although we may consider it evil... in the end it is for our benefit.
Likewise, it might be inconceivable for God to allow... or even create (our relative concept of) evil, but He takes full responsibility for it because just like physical pain, it serves a purpose, just like gravity and water serve purpose.
You may ask what purpose does a severely disable person would get out of the disability. I do want to slap any simpleton that says that disability teaches people to depend on God... especially when it's unnecessary, but likewise I think we tend to blame God for our relative quality of life... rather than enjoy every minute of it... even in pain.
We are born in pain and suffering, literally, our mothers have to go through severe physical suffering to give us birth. Yet, it does not stop them from giving us life. You may think that it would be unnecessary, but likewise imagine a world of perfect humans with no concept of evil, who don't experience any kind of pain. Without pain and "evil", our knowledge and purpose tremendously limited.
Likewise, our knowledge of God who is good can only exist in contrast to knowledge of evil. If everything was wonderful, then would it really be wonderful and how would you know that it was wonderful?
Above all, I think that all of us should learn to appreciate God apart from any religious concept of Him. If we shelf all of the "religious material" that tells us who God is... what do we have?
If you are willing to believe that the existence was created by a super-natural being then from simple observations you could say that:
1) He took diligence and pride in His creation by providing a diversity, purpose and balance.
2) He instilled the concept of beauty and purpose in a world that we live while striving for the best, and not the concept of nightmarish world that we are confined to as slaves.
3) On top of purposeful activities He gave us ability for pleasure... laughter, sex, love, and friendship.
Even if you shelf every other religious idea of God with no life after death and salvation concept... the life is still very AWESOME! And I hardly look at this world as a hell on earth. Sure, there is suffering and pain... but even in pain there's joy and hope and moments of happiness that I would not simply wish away for non-existence.
I think that as Christians we tend to overdo "gloom and doom", and I think it's because of our view that our suffering is necessary for the atonement of our imperfection. Thus we tend to gravitate towards the view that this world is a giant toilet bowl not worth saving or caring about.
And partly it's us to blame for portraying God as a "tyrant" that requires blood for our shortcoming... and if that's the reason that you don't believe in Christian God, than I don't blame you.