Just my opinion, and view points from my experiences.
For me it seemed we come here to gain true experience, learning and advancement in our journey of being God-like. The Angels and other beings in Heaven don't really know what it's like to actually know the things we learn here on Earth. Like I said before, they are naturally brave, but they are not courageous in the human sense. They don't really have as full of a learning that we do. They are more like animals is some ways. They only know & do what they're programed to do pretty much. Anyway, I believe that's why we come to Earth, to actually attain something that we would nevr attain in Heaven. I don't look at it as dark, although it is dark compared to Heaven, but I think it's better to look at it as only a place of attainment. Just like we never know what it's like to climb a mountain till we actually climb one. We will never know what it's like to be rejected in Heaven, and we'll never know the lesson from that experience until we experience it. There are limitless lessons to learn like that. I look at Earth kind of like a play ground where we come to learn and grow. When we get back to Heaven we can all smile and laugh from our experience here on Earth.
With my experience, I didn't see anyone but God and I. I did sense Earth had kind of a bubble or something seperating it from the rest of Heaven around it. The Earth was kind of like off limits. But unless it was really important, which no silly little lifetime is really, I couldn't go back to Earth to tell others I was alive.
I'm wondering if this lesser God you mention was one of the lesser beings in Heaven. There were things I didn't see but could sense on my journey. There were lesser beings I could sense.
There were other deminsions where others, people and other beings like Angels and who knows what were, and I could go there if I wanted, but didn't. Everyone I ever knew was there, but I never went to them. I kind of wanted some time to readjust back to Heaven, but I knew it wouldn't be long before I went back to earth again. (Even though time was meaningless there) It seemed I could go back to any age on Earth if I wanted. And it didn't really matter anyway, because before you knew it they would be with you again. But I really learned how time is meaningless. The past, present, and future are all the same when it comes ot living in eternity.
Also you mention the darkness. Remember everything came from the darkness, even Heaven right? God created the Heavens and Earth in Gen 1:1 Then created light in verse 3. God created plants in verse 11 and then created the sun in verse 14. So that first light wasn't the light from the Sun. I believe like you, that there's a light without heat, meaning no UV rays in that light. Light is a strange critter for Science to chew on. It seems to be alive in some way, just like water. There is an incredible energy for Science to yet discover that's going to turn their world upside down.
I don't look at Eath as learning black. I look at it as having to have black to learn light.
In my experience God didn't make me do anything. It was all my choice. It was like Heaven is a play ground too. It was my choice if I came back or not. My life flashed before me in about 3-4 seconds but I experienced each event good or bad in real time, but there was no judgement. God basically said "Good" and then basically said to go have fun now.
We remind me of kids being dragged down a path kicking and screaming all the way and when we finally get to the destination we stand in awe wondering what all the fuss was about. Have you heard the saying The only difference between a flower and a weed is a judgement? That's the way I look at experiences in life. There's something to learn in most events. It's all good in my book even though it may hurt, and sometimes it has to hurt and hurt till you learn the lesson, then it all disappears, and you smile in the end along with God. There are events that have nothing to do with your learning, some are just natural events that have nothing to do with our progression. And sometimes events that don't make sense to us aren't ment for us too. But I believe it's still all good weather it's a lesson for us to learn, or natural events, or a lesson for someone else to learn.
Like you said too, we choose the lessons we want to learn when we come to Earth. We leave it totally up to God on how to acheive that. Imagine trying to do that for each person in the world. Pretty complicated isn't it? But the drunk laying in the parking lot where you work could be there to remind you to not drink. This person could be willingly doing this for you, learning service to others, or self-scarific, or just learning what it's like to live of life of addiction to somehting other than God. A person in prison could be there for various reasons too. How could we possibly know for sure. Sometimes I think it might be possible to know, but who knows for sure. I think that's why it's best to just reflect the glory of God without our judgements changing what God intended. That's mastery in itself.
I think it would be really nice to be an Angel type being, but I think what God has in store for us is even greater. So I will keep driving over the humps and bumps along the road God has planed for me. Think of how much joy there will be after the journey! WOW! I think it might be enough to cause a universe to explode into existance. Kind of makes you think doesn't it?