Well, no problem at all. I'll try to answer to the best of my abilities:
1) Soundstage is larger on BH, but Fiio E12 is more airy. Sorry, I wish I could give you a different answer, but that's just how it is. The difference in soundstage between E12 and BH are actually pretty small. And BH would definitely lag behind if the SF switch and LF switch are not engaged at the same time. When SF switch is enabled, BH matches E12's soundstage, and the LF switch allows BH to have slightly more distinct instrument separation. But otherwise, I think soundstage is pretty similar between them.
2) No, decay doesn't hang around longer on E12. It's about the same as BH. E12 has an edge with bass decay because it can boost sub-bass frequencies, giving more rumbles, but without congesting the sound.
3) Layering is much better on E12. Bass and midrange are very detailed and articulated on E12. However, E12 doesn't try to bring out details with cymbals or any instrument that extends to high frequency.
4) And here is the reason: I think E12 has slightly more high frequency roll-off compared to BH. Both the SF and LF switches on BH boost treble as well, so it's quite a night and day difference. Even without those switches, E12 still has slightly less treble extension.