We know the extraterrestrials are cut off from their own higher self, are they also cut off from their own deep subconscious? Is this how they can be unaware that dark spirit attachments affect them as well?

Both things are true, so they share the difficulty of the hapless human individual unable to connect to their higher self and thereby get divine support from the soul very directly from their normal guidance, as well as having a corrupted link to the deep subconscious so it cannot be heard by the conscious mind and give any support and help with greater understanding of what it struggles with, and this prevents any kind of assistance and guidance, even from the conscious level of the mind that would otherwise give reassurance and seek solutions to deal with what was going on if only it knew. This is the greatest source of difficulty for people across the board with all manner of trouble in life on a personal level as well as in the workplace and in society at large.