It says friendly, but it really means anyone's planet but yours. There are supposed to be used to help your allies planets, so sadly you can't use the bonuses on yourself. Your only option to stop the allegiance decline is to either build more culture buildings yourself or to park a capital ship(s) over the affected planets. That or have an advent ally of your own send one of their envoys.

Yes it is, though I don't consider Infected Mushroom to really be that representative of Goa except for their earliest days. I associate them far more with psytrance, though most people do group the two together. IMO, Astral Projection, Etnica, or Man with no Name are probably better examples.

Yeah I have heard a bit of their new album, certainly more interesting than anything else they've done recently. I like a few industrial subgenres as well, and I've heard Front Line Assembly on the radio before, might have to listen to their new album too.