AFAIR ( from Aradans guide on twc ) discipline speeds up the regeneration of the morale loss through whichever reason - that´s why the units might be weaving, but then switch to shaken quite fast, while impetuous ones need longer to gain their confidence, and therefore easier to rout.
What do you mean by "upgraded to.." ? The moral boosting of those temples or other buildings? I think it´s somehow broken, no one seems to know how it really works, since those values aren´t shown on the unit cards like other stats.

Training indicates how tight units are grouped in their formation, though i don´t know, maybe they really perform better changing their formations ( from my, subjective, experience, it´s the command ablilities - aka stars - of the general, which make them follow orders better ).


Also, iirc, it´s the lethality of the tired units that drops, not their actual attack stats, but i might be wrong....