1. It may well do, but if the argument is that the Scottish Highlands and Islands are particularly remote and they want to subsidise economic development then they may want to maintain the exemption for long haul flights. It's harder to justify though.
2. I'm more than a little surprised but I can't understand how else base fares from INV would regularly be lower than from GLA, ABZ, etc. (OK maybe ABZ has oil companies funding a lot of flights but that can't be the whole story, can it?) I'm sure the selection of INV is influenced by the lower APD, too, but again - that can't be the whole story.