Falsifiability isn't empirical validity

@UnlearningEcon links us to a discussion of Popperian falsification here. Here is an earlier post and it's an interesting read. However I think the discussion confuses falsifiability with something that is maybe best described as empirical validity. At least if I understand what the discussion is about. The original author states:

Falsificationism has only two little problems: neither real scientists apply falsificationism, nor should they. If the very concrete 19th century astronomers John Couch Adams and Urbain Le Verrier had applied abstract, manichean falsificationism, (1) Newtonian mechanics and Kepler's laws of planetary motion would have been unfairly falsified, and (2) Neptune would not have been discovered. One can only imagine their dilemma: stick to the recently "falsified" Newton/Kepler or go back to the also falsified Aristotle/Ptolemy?

Emphasis in the original. Newton's laws are essentially a statement of the conservation of momentum and energy (and the definitions of mass, momentum and energy). Quantum mechanics adds expected values to these, but sufficiently accurate experiments weren't available at the time to tell the difference. I don't recall any violations of these principles measured at the time, so I am not certain what evidence was falsifying Newton's or Kepler's laws -- plus both used to this day. Newton calculates many things in the course of the Principia that are compared to experimental data; for example, he calculates the motion of comets observed by Halley and even the mechanism generating the tides. These are falsifiable in the Popperian sense -- they say the universe will behave in a certain way and not another. Neptune was discovered because the predictions of Newton's laws were off without the planet. This has nothing to do with the principle of whether Newton's laws are falsifiable (they would be falsifiable regardless of the existence or subsequent discovery of Neptune). So I do not understand the discussion in terms of falsification here.

A commenter named Hedlund adds:

E.g., Feyerabend, in Against Method, gives examples of theories that were by all appearances falsified, yet still advanced our understanding (and in some cases were later vindicated). In other words, falsification must be flexible and open to calibration rather than naively absolute; no theory is consistent with all facts.

A theory that was falsified is a fortiori falsifiable, and therefore science according to Popper. There is no conflict between being falsified (empirically invalid) and advancing understanding.
Falsification has nothing to do with a theory being "falsified" or its empirical validity. Falsification is about a theory having the capability to be falsified. All empirically invalid theories are falsifiable and hence science in the Popperian sense. Falsification is fairly metaphysical -- it is about the potential for a theory to be empirically invalid in some universe.
I think an example would be good here. A physical "theory of everything" isn't falsifiable in the narrow sense in the quotes above -- no experiment should ever prove it wrong because it is correct. But it is falsifiable in the Popperian sense -- for example, the theory of everything should predict zero macroscopic violations of momentum conservation. Observing non-conservation of momentum would constitute a path towards being falsified and hence Popperian falsifiability. We can't never prove it empirically invalid (falsify it) in our universe, but there is a conceivable universe in which there is some violation of the theory.
Additionally real scientists do consider falsification -- at least if they ever consider how to experimentally test their theory (which they should). The theory has to posit states of the world that will not occur. If a science is an experimental one (particle physics), it can help bring about those states that can't happen according to the theory and therefore demonstrate it to be empirically invalid. If not, the process of gathering evidence is harder (astronomy, economics).
Falsifiability is not in any way related to the idea that "all models are wrong" (which is about simplicity -- or better yet, complexity that can be supported by the quantity of data available). It is related to the "no true Scotsman" problem -- pseudoscientific theories have a way of explaining away any falsifying results (empirical invalidity) and therefore aren't falsifiable.
So a hard-nosed approach to falsifiability wouldn't have caused any problems in the history of science as it exists on Earth (maybe we can construct a case where it would be a problem -- I'm not fully versed on the critical takes on Popper). All scientific theories I know about are falsifiable. So are many economic theories. Second, empirical validity/invalidity is not the same thing as falsification. If you are considering empirical validity, you've already answered the question of falsifiability.  Finally, real scientists do consider falsifiability.
I wrote a bit about falsifiability before in a post titled  Falsifiabilité, simplicité, succès ... ou la mort. A good set of heuristics is that a valid theory should in general 1) be falsifiable, 2) not be too complex to be falsifiable, and finally 3) not be falsified. If you want to drop one or more of these, you better have a convincing explanation.
Economics has tried to get around these from time to time. For example I once read this line and shuddered: 

I recall Bob Lucas and Ed Prescott both telling me that [empirical tests] were rejecting too many good models. 

I think this was trying to get around number 3 in favor of number 2 without any convincing argument. But at least RBC was falsifiable -- it was falsified! Market monetarism isn't falsifiable as far as I can tell, violating number 1. The information transfer model is fully falsifiable and it has several predictions that should eventually show it. So there's me: a scientist considering falsifiability.

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Update 11 January 2016:

Here is a good link for Popper:

http://plato.stanford.edu/entries/popper/

Some good quotes:

This elucidates the nature of science as Popper sees it: at any given time there will be a number of conflicting theories or conjectures, some of which will explain more than others. The latter will consequently be provisionally adopted. In short, for Popper any theory X is better than a ‘rival’ theory Y if X has greater empirical content, and hence greater predictive power, than Y.

...

What, [Lakatos] asks, would have happened if Galle had not found the planet Neptune? Would Newtonian physics have been abandoned, or would Newton's theory have been falsified? The answer is clearly not, for Galle's failure could have been attributed to any number of causes other than the falsity of Newtonian physics (e.g., the interference of the earth's atmosphere with the telescope, the existence of an asteroid belt which hides the new planet from the earth, etc). The point here is that the ‘falsification/corroboration’ disjunction offered by Popper is far too logically neat: non-corroboration is not necessarily falsification, and falsification of a high-level scientific theory is never brought about by an isolated observation or set of observations.

I've talked a bit about Lakatos before.

This latter quote gives me the impression that Popper hadn't really delved into science so much as into defining pseudoscience (particularly Marxism and psychoanalysis).