Your first set of sentences are interchangeable. The first sentence in your second set is more natural. You could simply say: Wasn’t it worth it? as an option.

They mean essentially the same. As always in a language, there is an ever so slight change in connotation when you express it differently. @"...want to sell": They have the plan and intention of selling, might have taken steps in the direction. @"...willing to sell": They can be persuaded to sell it. For example, if I want to sell my car, I might put in a sign saying so. But even if I didn't want to sell my car (had no prior intention of doing so), I might be willing to sell it when someone offers a good price. - I hope that makes sense. "Wasn't it worth everything" - never heard it used like that. Though not wrong as such, it just sounds a little off, can't quite put my finger on it. Hope that helps!

Yes they mean the same thing.