DC-circuit with N-JFET transistor
You're a little off on your calculations.
Vgs =/= -Rs * Id. Vs = Rs * Id. To find the gate Voltage, you need to know what the current draw into the gate is through that 1Mohm resistor is. Then Vg = Rg * Ig. Vgs is then just Vg-Vs.

Use that to solve for Rs and then Rd and I'm sure your simulation will be much closer to reality.