I, a native speaker, would panic, too, if I had to use one of those "textbook phrases of obligations" to say something as casual as "After doing A, you gotta do B." to explain something about a game. I would sound like a robot if I used any of the three phrases you listed.
What many native speakers would say to a friend in this kind of situation would be ...
This しなければなりません just means "must", "need to", "have to". And that's the only meaning of しなければなりません.
An Indian person who came to the meeting said, "[I] have to make the air (of India) clean after Japan taught a lot of things to [me]."
An Indian person who came to the meeting said, "[We ...
You don't really have to do anything special- just put the final verb (adjective) in the past tense.
学校まで走らなければならない - I have to run to school
学校まで走らなければならなかった - I had to run to school
This works with all three of the constructions you mentioned.
ならない = ならなかった
だめ(だ) = だめだった
いけない = いけなかった
Of these, I see ならなかった the most by far, but the other two ...