Seems you are right on track however.
First, the obvious: from your description, it seems you generate the
correct map, but did not "load" it into the system (this is done either
automatically at boot by copying the new .map file into /etc/keymap, or
manually at any time using the loadkeys(1) command.)
Otherwise, I agree with you that "73" (set 1) key is specific to the
Brazilian keyboard (just left to the right shift key in the normal
layout), and indeed it is lacking from the abnt2.src keyboard, a defect
MINIX should correct when the freeze ends. Also missing is the "7E" key,
which is located on the keypad, between the + key and the Enter key, and
which 7E (126) key should emit a '.' character when the 53 key between 0
and Enter should rather emit a '.' character, isn't it?
Antoine