Ok so the first thing would be to make sure there is nothing left over from your other attempts.
In the terminal please mount your EFI partition as follows
then
Code:
sudo mount -t msdos /dev/disk0s1 /Volumes/efi
Then open Finder and in the left pane you should see EFI listed. Click on that and in the right pane you should see just one folder called Apple. If there are any remnants from your previous Windows installation attempts there may be folders called Microsoft and/or boot. If these exist you need to send them to trash.
Leave the Apple folder untouched!
Ok close that and open Bootcamp Assistant and let it re-partition your drive as required but do not reboot yet!
After BC has partitioned please run this command in the terminal again
and see if it looks like it did before (in your earlier post when I asked you to run it).
If it looks the same let BC reboot the system but when it restarts into the Windows installer don't start the installation yet.
Instead press shift + F10 keys and a command prompt will open up.
In that window type
diskpart - hit enter
list disk - enter
select disk 0 - enter
list volume - enter
Now have a look at the output and note your (probably) second entry. It should be your EFI partition and it will have no drive letter attached - i.e. just a FAT32 volume with a volume number (probably 2 but it could be different)
type
select volume X - hit enter (where X is the number of that EFI partition)
assign letter=B - hit enter
exit - hit enter
close command prompt window
Now start the Windows installer as normal.
You may need to re-format the Bootcamp-created partition so that Windows will install (but you've done that before).
Hopefully you won't come across the same error as you did previously.
But if you do see that same error message, power off the machine immediately by holding down the power button. DO NOT let it roll back the changes by clicking on the OK button.
Then let me know that this happened, please.