I agree—added these links to my post

Why is (1) obviously false?

I don't think this premise is as intuitive. For example, if someone said that a quadriplegic should have saved a nearby drowning child, then the objective appears immediately this it wouldn't have been possible and so the "should" claim isn't reasonable. On the other hand, if you say that the quadriplegic should avoid intentionally drowning the child, I don't think that's clearly nonsensical or false.

Yeah I've argued that banning lab meat is completely rational for the meat-eater because if progress continues then animal meat will probably be banned before the quality/price of lab meat is superior for everyone.

I think the "commitment" you're describing is similar to the difference between "ordinary" and "constitutional" policy-making in e.g. The Calculus of Consent; under that model, people make the kind of non-aggression pacts you're describing mainly under conditions of uncertainty where they're not sure what their future interests or position of political advantage will be.

People should be free and equal

You opened with an assumption that your described audience ("progress studies people, economists, techno-optimists, anarcho-capitalists, proper libertarians") largely doesn't share. Why should people be equal? What sense of equality do you have in mind?

More generally, you make a bunch of undefended claims, e.g.

• You say that when one side has bargaining power over another, that's bad per se, but it's not explained why
• You say that when there is more wealth concentration, that leads to less freedom "empirically" but you don't present any empirical evidence  
• You give Elon Musk buying Twitter as an example of the negative influence of billionaires, but in fact the Twitter Files reveal an apparently more serious threat to freedom from the state, whose power is actually counterbalanced by wealthy individuals

It makes intuitive sense to me to say that if you have no way to do something, then it's nonsensical to say that you should do that thing. For example, if I say that you should have arrived to an appointment on time and you say that it would be impossible because I only told you about it an hour ago and it's 1000 miles away, then it would be nonsensical for me to say that you should have arrived on time anyway. This is equivalent to saying that if you should do something, then you can do it. 

The converse "Whatever ought to be avoided can actually be done" doesn't make sense because there's no equivalent intuition.

What fundamental confusions?

No I think Kant's "ought implies can" principle usually uses "can" to mean some kind of "practical possibility" that means "possible given your powers and opportunities" or something. And whatever is possible in that sense is also physically possible (i.e. "possible given the actual state of the world and physical laws"). So the argument is still sound.

Why? If you're taking as a premise that "Whatever ought not to be done can actually be done" then I don't think that makes sense.

Yes I agree to be clear.