I think you covered pretty much all major issues apart from one - emotional aspect of the change.
From my own experience, I can say one thing - that feeling that you want to try something different, new in your life - to start a business, start a family or just 'see what it's like on the other side' - it just won't go away. More so - the years will pass and you become more and more bitter.
It's very important to test yourself not only as an employee but as a person aside from what you do - because in this way you not only gain experience much faster, but it is 'tailor-made' just for you.
Another thing is the return to your old job - if, over the years, you have made yourself a valuable asset and not an faceless, average-quality drone who can be easily replaced - the door will always be open to you.
For me - personally - work was too important. Less than two years was enough to finally understand that work is just work. That I shouldn't approach it emotionally, it shouldn't stress me out to the point of running out of breath.
I have gained distance and calmness, and I have also become a better professional because I can 'infect others' with calmness:)
Plus I have had time to develop my own small business on the side. When it grows to the point where I can make a living from it, I will be able to leave my job this time with peace of mind and without stress:)
There is no ideal solutions, so you have to figure this for yourself, but I promise, you will learn out of it more you can possibly imagine.
It takes a good planning though. I wish luck to all 'Changers':)
Thanks for stopping by and providing a very detailed comment.
My pleasure!