As I said in my previous post, the two markets mostly move in lockstep. Whenever the two diverge, the arbs would come in and bid up one market and sell the other until the two converge again. So the question whether the futures can stray far away from the spot price is moot. That can never happen, at least not for long.We are getting close. I agree with everything you are saying. But I guess the best way to illustrate what I am saying is with an analogy of price controls. The government can set the price of bread let's say but a bakery cannot produce it because the cost of flour is more than the maximum price that they can sell the bread for. So then there is no bread. Likewise, if the futures price gets so far away from where spot price is, then there won't be any supply. So how can you have the future price saying one thing when spot price is saying that the only seller is two times higher? This would show the manipulation. And this is also why I think it has to be the spot price that leads and not the futures price.
Then the question remains: which leads which? Does the spot come before the futures or vice versa? For the most part, I concur the spot leads the futures. However, there can be times of vulnerability as pointed out earlier when the futures can play a pivotal role (eg. stop hunting, etc).
But bitcoin futures is a little different from other futures. With other futures, there's not a physical spot market where trading takes place. For instance, even though you can trade the crude oil futures like CL, there's no actual place for trading physical crude oil itself. Same for the index futures like ES. But with Bitcoin, you can trade the futures as well as its underlying.
Anyway, you need to understand this. The whales, who have enough resources to temporarily move the market, will likely trade all three markets at the same time: spot, futures and ETF. If I were a whale wanting to pummel the price down, I wouldn't just sell the spot bitcoin. I would go all in crushing all three markets at the same time. And that's called smart move, my friend, although some might call it market manipulation.

Ya just might get your wish.