There is no real answer to your question. The metal damage sounds fairly extensive and would be very expensive to repair back to new looking. The front end cap damage may be enough to cause leaks, even if you were willing to live with the looks. The leak in the back which has not been addressed would be of a big concern to me. How well the rear floor repair was done is also an issue.
To be quite frank, from what you say about it, I would be unwilling to buy it at most any price above salvage, but then I like a nice looking and performing rig. You may have different expectations. Which is why I say it is hard to answer your original question.
One thing many here will tell you is that there are many Airstreams out there, and you don't need to buy the first one you see. Take your time to look. You will also hear that, unless you love a project, buy the best and most cared for rig you can find, as you will pay a lot to have any repairs, even seemingly minor ones, done. A rig which needs no repairs or upgrading is often the best one, and the extra money is well spent.
Best of luck and happy hunting on your quest.