About the heighth of some skeletons............what about the Zulu tribe in Africa. They're outstanding in many ways - I think the average (at least used to be) around 7ft?
Of course, the Pygmies have already been mentioned - but it does show that a remarkable difference is seen in human size. Also, the dead person could have just been a oddity - like those which frequented circus side shows.
As for the group of tall skeletons - it could also be that the beginnings of that group were ostracized (or chose to marry like sized ones) - and went off to form their own group. Intermarrying. Very common.
The angels "materialized" - get it? It was like Star Trek. They shimmered for an instant, then gradually became present.
That's the explanation I was taught. After the flood, the angels weren't allowed to materialize anymore - thus the need to takeover another human. If they could materialize a body, then they obviously could materialize sperm. If we're making the story up - and we are - this explanation is as good as any other one. Make your own up!
Ohhhhhhhhhhhhhhhhhh, this could go on forever.....because there is NO ANSWER as it's make believe. Trust your child, when it's make believe - believe whatever you want. Well, that's the WT way too.
Merry Christmas!