In the days I worked in MIDI, I too would physically play slower at the end rather than edit the temp settings in the measures. It was just so much easier and required no editing.

MIDI didn't care. All it was doing was recording the placement of the notes in it's internal tempo grid. Since I played the midi parts live, and also added other audio parts, it didn't matter.

Trying to reverse engineer the tempo on something like that is really, really tricky. Especially if you are trying to compensate by editing the tempo settings. Not impossible but certainly not a fun job even for someone who knows how to edit midi and does it a lot.

If you can look at the midi part in a staff view format, you can easily determine if what I described was the way they recorded it. If it was, the next issue is, can you edit in midi? If so, and the underlying midi tempo is constant....If I understood correctly, you did say the song tempo remained constant throughout..... you can slide (edit) the notes around and change their duration's for those last few measures. Not hard if you know what you're doing.

This is relatively easy to do in a DAW.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.