#1
So I've been working with a couple riffs lately on my acoustic... It's capo'd on the 6th fret, and the main part plays around with an Amaj7 and Gsus4 (well.. relative to the capo).. that's what the main part has been for months now.. but just this week I've had a strike of genius (or so I thought) to make the next part... so relative to the capo on 6, the new part goes (*h=half note, q=quarter note, e=eighth note, s=sixteenth note)

||:Gb5 F5 E5 | B5 A5 B5 :||
h q q sssss e e (dotted q-rest)

This just struck me as bad... Because capo aside, the chords become the same as the verse of GNR's My Michelle... It took me a week to realize this... But damnit... Meh, Axl can bite it...
Go back to square-one.
#2
A chord progression cannot have a copyright. Many chord progressions are used very often by many bands and I will list some below. As long as your rhythm is different, or even the same rhythm at a considerably slower or faster tempo, you're fine.

Some Common Chord Progressions:
1. I IV V
2. I V vi IV
3. I IV I V
4. i VII VI
5. i VII Vi V
6. i III IV (usually done with power chords)