Hi, Erik,
I've got an alternate suggestion, one I've used with great satisfaction myself.
Don't mend it in any way. Copy it.
Copy it from scratch. Then compare your copy with the original.
Use it for a while. Then compare again. You are almost certain to notice things
about the original that you didn't notice when making your copy.

Have I read you rightly over time, that you have metalworking skills sufficient
to manage a copy of the blade? So keep the original as a storehouse of original
embodied craft wisdom, and copy it, and maybe in ren years copy it again with
better insight. And maybe the next fellow along will look at it and your copy
and think you got something wrong, and he can do his own copy and learn even
more. None of that will be possible if you "fix" it or "replace" parts.

A D-adze would count, I think, as a genuine cultural/historical piece of
heritage to be protected... well, if Scott says he has never been able to get
one, it must be pretty rare. So copy it.
Tom Conroy