OK I fixed this.
So I got into the grub editor and changed the name of the kernels manually to get it to boot. Then I did an ego boot update which failed. I then remembered the emerge grub part and did that. When I looked up it was like the matrix on my screen as a billion lines of code went by.
Why doesn't make change the text color to shades of green when i use the --matrix option??!!?
I used etc-update to merge /etc/default/grub changes. Now "ego boot update" worked, tho with warning I must digest.
Things I notice: the search line has updated disk ID, and it found the old kernels which boot-update never did.
Oh - and KDE doesn't start. /etc/conf.d/xdm has DISPLAYMANAGER="sddm" but there's plenty of --depclean stuff yet to be done.
So thanks for the help, guys, I can boot again!!