For the exec-path issue, I have a patch here:
https://github.com/emacs-mirror/emacs/commit/2c91d2c0fef162ecce87915863931bea47305eac;
this ensures running `emacs` from PATH on my system finds the right binary,
and lets emacs start up (there is a weird delay though, which may well be
my system being creaky).

The same branch that this change is on, I also have a change to build a
separate .pdmp file for the macOS app bundle - but that set of changes
isn't yet correct. It still picks up the wrong file name, still.

However, good news: One part of the bug is dead, at least (: