Before Exporting your Images out of zBrush, set Render to Best. This will Help to avoid Black Seams in Photoshop. Its an old Bug :( and never really solved.
Ok so I'm nearly done with the low poly and shader, just few Normal Edits to solve. Here's the current result: and for fun : Next step will be animation !
Thanks for the surprisingly rapid response you guys. :) Granted, the problem hasn't been solved but I really do appreciate people taking the time to look. pf
Yeah I think that was probably it! It looks much better, thank you! Shininess issue easily solved by adding a skybox, of course (as seen in another reply here).