How do I solve the input resistance of this BJT and MOSFET in series?
(not a direct answer)

I don't use the equations. 

I figure it out from datasheet plots and excel as I did for the diode.

How to model a real diode 1N4148?



Then I verified on Falstad Simulator  with my parameters

Since Ri load line at  BJT saturation or FET conduction has  50% factory tolerance , your choice of datasheets matters with overdrive levels.



Then show the ON diode curves here.