As for your second song I can give you some help:
If you searched for an overall tonality of the song I would clearly state that Bbm is the tonic. You can see it as aeolian/minor and Gb being the VI.
I'll give you an example to get the idea - play it on your instrument at home:
Think of this being in Db-major:
- vi - IV - I - V (Bbm - GB - Db - Ab)
Or in Bb-minor:
- i - VI - i - VII (Bbm - GB - Bbm - Ab)
Now go back to your song (also seen in Bb-minor):
- i - VI - i - II (Bbm - Gb - Bbm - C)
With the II-major you can not see it as a traditional mode because there is no minor-like mode that has a II-major except phrygian but it has of course a semitone between I and II. This tune could only be dorian or aeolian. In dorian there is no VI-major but rather a VI-diminished so it is out of question, too.
That leaves us with aeolian/minor and you have to interpret the II-major as an alteration, kind of fallacy as it were - but a nice one.
The idea of having a IV - V progression in Fm is also valid but for my perception the tonic-color of the Bbm-chord is way to strong to hear it that way. And the Gb as bII is even harder to interpret than the color of a II-major that is quite often used in minor-compositions...
So over the first three chords you can play a scale with 5 flats (Db-major) for the last one you have to choose yourself. Something like C - Db - E - F - G - Ab - Bb - C sounds nice or a D instead of Db...
Its 'off' anyway - so chose an 'off' scale... ;-)
Or ask Dom or Matt - they are always in for some crazy stuff...