Still has the stock carb I assume.
Mine ran just like that when I got it.
It is a first generation computer controlled carburetor and timing. So everything has to be working (sensors and vacuum stuff) for the computer to run the vehicle right, but unlike modern ones, it doesn't automatically tell you what is wrong.
You really have one of two choices. You can go through and test/fix all the emission control stuff (sensors etc_) so that the computer can run the thing properly or you can bypass the computer.
to fix and understand what can go after you bypass.
Tune up with better Ford parts.
Your brother is right, the air to fuel ratio is bad because the computer isn't properly controlling it. Timing is bad for the same reason.
Make sure you won't flunk visual emissions inspection by doing Nutter bypass.