1/ Vt is in the range of 0.02- 0.04V
2/ In reverse bias : The resistance increases when the current increases as the depletion region becomes bigger ( R in Mega, I in micro or nano)
3/ In forward bias : The resistance decreases when the current increases as the depletion region becomes smaller ( R in ohms , I in mili)
4/ You have only six equations : Id , Vt, Rdc, rac( two equations), rav.
5/ Please make sure that you know how to draw each model characteristics graph