Hmm...your idea seems rather interesting, but if I would, just offer a little of my opinion.
From this perspective, your main character being a protagonist, needs to have something above all the others, but it seems that he is a little too overpowered. A character needs to be a little more down to earth and relatable. In addition to this, it will help in senses of tension to build a climatic scene if he is actually killable. If someone is obviously not killable, its not fun because you can predict the outcome, the protagonist wins. Always. To make it vibrant, he needs to dangle on the edge. If not, then a key weakness. Something that can bring him down, brought in at the peak of a story. That can provide enough of a shock factor to spice things up.
Backstories can be used considering his past, but interweave it into the story. Dont chuck a chunk of text introducing him. Weave it in, paragraphs and chapters unveiling more about his storied past.
Might I ask what the story is going to be like? It would be very helpful to know what kind of experiences that your protagonist will be going through. It helps set the tone of the story.