I would have to concur with prepuce here that as far as I can remember the distinction made between a weak and strong acid was the completeness of the dissociation into protons and their respective anions in aq. solutions. The proton in HCL and the first proton in H2SO4 should easily be completely liberated in water (second may be slightly more difficult but not too much would be my guess). I would really appreciate correction on this point if I am wrong as this was learned when I initially started learning chemistry and remained a fast rule which was not reexamined??? Is this not the case?

Perhaps both myself and Prepuce are off beam slightly and Sedit you are referring to the attraction between the amine and the hydrochloride entities? That is an interesting suggestion but I doubt, considering the established history of the PSE molecule in medicinal preparations, that there is any amine left as a freebase when an excess of the acid is present. Worth looking into though, good suggestion!

More likely to impact proceedings in terms of association and dissociation is the interaction of the PSE from the polymer units. A sacrificial molecule here may displace the PSE from these polymers. 

Prepuce, i think any stronger chelating agent would break complex with PSE/EPH.
What it could be among OTC reagents, im not sure but i suppose :
glutamic acid(in basic solution)(that is widely used as sodium glutamate seasoning for chinese food),
thiosulfate(solution for infusion on pharmacies) that reduces Cu(2) to Cu(1) with further formation of thiosulfate complex of Cu(1)
maybe ammonia (not sure, pH may also play a role as 2+ charged PHE/EPH complex is less stable then 0 charged(the one that is possible to extract), and it may form either in neutral pH, or only in alkaline, i dont know, so better to use not too high pH).
Maybe diols like sorbitol or sugars in alkaline media also.
The indication of complex destruction(it is still quite stable, not all chelators may suit) could be the docolorizing of organic layer(coloured complex with amine) with some chelating agents that form insoluble in organic phase chaletes(glutamic acid, ammonia, thiosulfate, maybe citrate etc). At the same time amine would be transferred to organic layer

i think that additive you are talking about is a polymer known as poly vinyl pyrollidinone
it is nitrogeneous and bears a ketonic oxygen.
so in basic conditions it will form a shiff's base with the amine and in acidic conditions it is protonated and water soluble.
hence it "follows the amine around wherever it goes" as you stated.
so the strategy would be to get rid of the polymer by boiling it in perchloethylene first, then extract.
maybe the state of the art has changed over the years but that was once of the main strategies employed.
perchloroethylene is preferable overr dcm and chloroform because the amine hcl is soluble in both due to polarity issues.

why not ion exchange resins?

It seems as though a strong base would again serve to form the freebase and be rid of the copper, but I'm not sure about that.

no, base won't do that. acid - yes, as you said base is used to generate a free base, but as you can see the complex is being extracted into ether, that means it is not charged. That means, base also deprotonates 2 OH groups to make them O-, so the total charge of complex is 0. This may require a very high pH, like 13+, or it may be taking place at pH just above 8, i dont know.

yeap you are right, but chelate may consist of 2 PSE molecules, PSE ligands make it more hydrophobic, and OH deprotonation provides a neutral charge, so it can be extracted with ether  

PSE combined with copper forms a complex with a charge of zero

Yes, there are probably also 2+ and 1+ charged chelates at lower pH, but at high pH charge becomes 0

which should release it from the grip of any polymers/surfactants or the like.

yes

This complex is soluble in ether, and that would be the preferred method of extraction.

Yes, it is soluble in ether but in water it is soluble too. The resolution value(or how it is called in extraction, i dont remember exactly) that is a ratio between concentrations in organic layer and water, may be not that high for this complex. If it is even 1/5 (ether:water), or even 1/25, it is sufficient to colorize ether layer, so for analysis it is ok. But for you it means using gallons of ether for complete extraction. I dont know what this resolution value can be even approximately, maybe it is sufficient enough and the substance can be fully extracted with several portions of ether. There should be data on resolution values for inner-complex compounds(chelates charged zero) in literature, but i am not sure PSE or EPH complexes are there. You may probably use similar hydrophobic structures to estimate resolution value. But the best way is to do it experimentally, by changing an ether layer for a new portion of clear ether. If resolution value is high enough, the colour would be much less then in previous portion. You can also add saline compounds to increase a resolution value. Still if there is no possibility to extract the chelate completely, it does not mean using it for isolation is impossible. For example, this can be used to get rid off other amines by extracting them at pH values when PSE complex is charged 1 or 2+ and thus not extracted.

Once extraction is complete, the complex would need to be treated with monosodium glutamate to break the PSE bond with copper, which would form another compound that wouldn't interfere with separation of the PSE.

Yes, this hopefully can be glutamate. Zero charged complex is still quite stable, maybe more stable then glutamate, better to try at pH values at which complex is charged 1 or 2+. You can try to find data on these complexes stability in books, if there is no such data on PSE - you can assume that stability of monoethanolamine copper chelates is quite similar. Btw, monoethanolamine, if you can find it, would definitely release PSE. Edetic acid as well.
      

What defines a complex? Does the Cu actually form a covalent bond with the PSE, or is something else happening. What are the chances of breaking this bond without damaging the PSE in some other way? 

There are plenty of books about complexes, or having chapters dedicated to complexes. Better to start with inorganic chemistry books(basic theory, nature of bond, geometry(for inorganic ligands mostly) and analytical chemistry(chelates and their stability, inner complex compounds, resolution value etc). The bond is donor-acceptor, it is not covalent(otherwise, how valency of copper can be 4?). No chances of breaking down unless you use extreme conditions. Moreover, in complexes, ligands generally become more chemically stable then without metal, this should be fair for PSE as well. Of course there are exceptions, but without harsh conditions and oxidizers nothing should happen.

How likely is it that all of the Cu can be removed from the PSE? It wouldn't do to have traces remaining.

This is quite possible. That should depend on a method of breaking down copper complex, and a ligand used for that. If the difference between stability of these chelates is quite big, like 10^5, then there would be small trace of copper, if it is not that high (like 10^2) you can get about 1% of copper chelate in your PSE if you use equimolar amount of chelator. If you use 2 fold excess, then it should be 0,01% of copper chelate. But maybe simple recrystallizing can diminish it even more then using excess of chelator. Of course, better is not to administer such PSE or EPH or ephedrone, unless an appropriate analysis of copper presence is not been done(maybe flame analysis? it is having a rather low threshold of determination of copper if i'm not mistaken, better to inquire in literature what can be used). Otherwise it may be hazardous, maybe not that hazardous as Mn, but this should be inquired. Good question.