Some questions:
-What is the deal with Black Skye. Is she really just a skilled warrior and nothing more? With three shows worth of hyping and Alexandria risking the lives of the 5 fingers, you'd think it would be some unstoppable force, rather than a skilled individual that doesn't know what she wants and one that almost loses to DD alone. Or someone with a special power or something.
I believe the extent of it was the strength and durability increase she got similar to Luke Cage, and Jessica Jones. And the whole black sky prophecy was never explained outside of Alexandria making it up, and they didn't developer her either. So it was all meaningless in a way.
-Why did Elektra not have a hearbeat and why did she lose her memories (to some extent)? The five fingers of the hand do not seem to have these problems?
They never explained the heartbeat in relation to the other Hand members. In DD, they were able to mask it, but it sounded like it was from training, not because they were dead. The memories were deliberately wiped, at least that is what Alexandria said.
-If the hand warriors can hurt Cage with a punch, couldn't they obliterate DD, JJ, and especially IF with a mere hit? Or are there some rules to this ki stuff I am not aware of?
We never really saw Luke get hurt with any of their hits. The only time he knocked out was after stick drugged him, and was hit in the head by super powered Electra.
-As for the Hand, I am confused and I feel I likely missed some crucial dialouge due to me not paying attention for the last three episodes: What is the deal with the dragon bones? How did the hand know what was beyond the wall/door? Was this the "resource" Alexandria kept talking about that they ran out of (as in, the same stuff they had before)? And why was New York in danger? They said the removal of the "resource" would mean destruction for New York. Initially I thought their goal was to destroy New York (like they did with Pompei and the likes), but now it seems like a side effect of... removing bones?
The dragon bones can be ground down to make the resurrection substance. They probably knew what was down there due to being around when the city was built, but this was never explained. It was never fully explained, but the removing of the bones would break the foundation of the city causing it to collapse. It was implied that all of the other fallen cities met with natural disasters because the dragon bones were removed. The why is not delved into too much. Maybe we will get some better writing in IF 2.
-So aside from gaining immortality trough those dragon bones, does the Hand have an ultimate goal they fight for when they are not searching for "resources"?
Just immortality and running the world. Some of them wanted to get back to Kun Lun, how they would achieve that is never explained. Show was super vague and poorly constructed around the hand.
-Where are all those ninjas? Did they run out of them post DD/IF?
The ninjas were mostly killed off during Daredevil season 2. They ran out of the resurrection substance. Plus Nobu headed the ninja portion of the hand under Murakami. Murakami was implied to attack directly when he was involved. So maybe they can bring the ninjas back later on because they were not involved. Either way, it was most likely due to budget. The same reason we did not get Punisher mowing down a 100 of them with a mini-gun at the end of DD S2. Better writing could have fixed a lot with this show and the lack of a budget.