Thank you for writing.
I was planning to do followup post after this one about the full first ego death experience, in which I intend to cover the topics you've mentioned. I'm really relieved that at least one person is interested :)

I'll give some quick answers now, but I will post the full story and context on Sunday/Monday.

The initial experience lasted 4 days, I feel like it could have gone longer but there were certain events that pulled my old ego back around that time.

I have an extremely mindful close friend who is in the same position as yourself. He is able to reach the edge of a high level of awareness to the extent where he can see the opportunity to just let go and jump. He never has, but he also gains insights and understanding that have positive impact.
There was a lot of fear the first time, and even when I do it now, there still is. There have been a couple of times where I have also come to the edge and ended up stepping back into the current state of being.

As for what happens to the fear once you step over, well... I'm just thinking about it now. The fear is certainly a manifestation of the mind that you leave behind. I don't recall anything other than a near immediate removal of the fear. I think the reason I'm having trouble recalling is because the frame of mind is so altered in that moment that the concept of the fear as it was no longer makes sense as a question in the context. It is hard for me to speak for that version of myself when I am not in it though.

The new mind and self we become is different from who we are just before the event, the concerns are not shared. I suppose there could be relief in knowing that the self that fears the worst won't be around to ask questions once it is gone?

Thank you for the thought provoking questions! It has raised a point I wasn't considering previously. I hope that I'll be able to provide more clarity with my Sunday/Monday post. :)