I agree with most of what you write.
In terms of Israel-Palestine, I think the question is the following. If a single state settlement would be more desirable - and I agree that it would be, for various reasons (eg you could solve the question of the descendants of the refugees more easily) - ok, but how is it going to happen?
Is it conceivable that the Israelis are going to dissolve themselves into a common state with the Palestinians? That most Israeli workers are going to be won to this?
Isn't it far more likely that a majority of Israeli workers could be won to forcing "their" government to withdraw troops, evacuate the settlements, give the Palestinians a really independent state and so on? This may be a long way off, but it seems to me qualitatively closer/easier than most Israelis be willing to dissolve their separate nation state.
The only way I can see a single state realistically coming about, except as a step forward after the Palestinians get independence and the two nations live alongside each other, is one side conquering the other completely. And of course such a result would not be democratic, secular, truly binational etc.
Of course, there could be a revolutionary wave across the region which will pose the problem differently. But, firstly, we should be wary of assuming even revolutionary working-class struggle will automatically solve the national conflict: in fact the national conflict could be the rock on which it crashes. And in any case, don't we need a more immediate democratic slogan given that no such revolutionary wave exists?
Sorry if I'm repeating myself!