Please understand that you are asking questions about a ceremony that is considered the most sacred of our ordinances and that does involve secrecy. Before I give you my answer, please understand that the purpose of the secrecy is not really to hide things others shouldn't know or wouldn't understand. The purpose of the secrecy is to teach us a very valuable lesson in integrity. To make my point: I once asked a friend of mine, a convert to the LDS faith, about the ceremonies of the Masons, of which she was a member. She wouldn't reveal what she had promised to keep secret even though she was no longer a Mason --- she understood the point.
Yes, there were penalties as part of the Endowment Ceremony prior to 1990. No, I will not tell you what they were because I covenanted to keep those things secret (I was endowed in 1984). Penalties were not an uncommon thing in many societal ceremonies of the 1800's as they were a very visceral way of helping generally uneducated people to understand the sobriety of the covenants. There is no specific scripture that teaches the need for the penalties. Indeed, there is no specific scripture that requires the secrets. There is a scripture that teaches why the Church implements procedures that help teach lessons in integrity. D&C 84:54-55:
And your minds in times past have been darkened because of unbelief,
and because you have treated lightly the things you have
received—which vanity and unbelief have brought the whole church under
As people became more educated, the need for the penalties diminished, and were finally discontinued. We no longer need such blunt tools to teach a well educated membership a lesson in integrity.
Having said that, I would like to point out that the person who captured the video has failed the test of integrity and didn't understand the point of the secrecy at all. Why should the Lord trust such a person? Why should we? It is also worth pointing out the disrespect shown by those who have promulgated the video. Doesn't the Golden Rule teach that if you want to be treated with respect, you should first show it? Many people interpret our reluctance to discuss our Endowment Ceremony as proof there is some nefarious intent. Nothing could be further from the truth. If we suggest that the covenant of Baptism is made in our spiritual infancy, granting us time to learn how to stand before the Lord with honor, then the Endowment Ceremony serves to make our covenants of obedience in our spiritual maturity. We should not treat that with lightness, but with considerable respect and solemnity before the Lord.
It is my sincere hope that you understand my answer. You've asked a delicate question, but I don't believe you are looking to disparage or mock. And so I've provided what answer I can to respect an honorable query.