Hello:
First of all there could be salt because, unless you wash with some plain DH2O last there will always be some sort of leftover sodium ions, these will make salt upon acidiffication. With P-Fed taste is really not a good thing to go on, many things in the pills, including the antihistamines, have that very bitter/nasty/sour taste. Unless you have been cooking alot, taste wont be of much help.
As far as your pill extraction goes, on the whole it was done very strangely(weird choice of solvent, and weird order of washings). I belive I know the brand of pill you used, and to remove all the shit well, the soaks and boils need to be done in a certain order. If the pills you have are the name-brand version(with Povidone), you should have used your Turps for the soak, not MEK. If they where the generic version(no Povidone), Xylene should have been used. After your soak you should have done a Acetone(or MEK) boil or two to remove the rest of the Povidone(Povidone gets nasty at temps of 104C and up). You can still do your boils if theres a sugar coating on the pills, you just cant use Xylene with its ultra high BP, Toluene,Naptha,and Mineral Spirits are usually allright, and it does not have to be boiling, usually pretty hot is ok. The yellow color you described was most likely PEG, those pills are packed with it. When you say you removed the HCL, I hope you mean you boiled it off and not decanted because, that will certainly cost you some yield. I read your other post about using the Tetra Trap, why did you change your mind to this instead? The TT would have been much better for you probabaly, it quite user friendly.
Now as far as testing the "white fluffy stuff", you could just eat some of it. Nothing in the pills is deadly or dangerous, eating a small amount would let you now what you got, speedy=P-Fed,Sleepy=Antihistamines, nothing=Binders/Fillers. I will probably get shit for suggesting that but, it is an easy way. It only takes the tiniest amount of antihistamines to feel an effect, usually twice the amount of the boxes recommended dose so, start with a ultra tiny amount.
Oh yeah, if it turns out you did in fact fail, just remember its not the end of the world and, we all failed our first times(three times for me). So stick with it and keep learning and trying, anyone can be good at this, it(like all things) just takes time,practice, and above all else the desire to never stop learning.
Good luck fellow Bee, may you always be prosperous.