What did you adjust the rez in the ini to?
Tried to manually set it to 1360x768, but when starting the game, the combo reverted to the default value.

These things are related to Antialiased textures. Don't know if it is a bug in Apshyre, but when textures are antialiased, the border pixels get "mixed" with memory "pixels", because they have no neighbour pixel in the texture.
Dunno about the internals specific, could be just a missing clamp, clamp_to_edge or equivalent attribute missing for the texture.

Main music became silent? First time I hear of this. Is it just stopping or fading out volume?
It made crackling noises (like VerneX), and then stopped. Only splash screen music did that.

How are other games working using BASS?
Dunno, are there other PGD entries using BASS? I tried an FMOD game during the test session and it no issue. I'll try running some BASS demo.
Are you using environments?

Are you sure there is no problem with your sound card/drivers?
It's a built-in AC97, not a discrete card, latest drivers AFAICT, but those aren't updated often.

I know that it is hard to aim air targets.
Actually it was a reference to the low framerate, which made hard to hit ground targets - the tanks in the pen

I will make them shootable with machine gun, too.
Shootable with mgun or "pushable" with the tank should do it.