Yes, you are correct. Additionally, if you do not wish to include the material dispersion of the non-linear material from the Material Database, then you can use the (n,k) material with index 2.49 you defined earlier as your base material. But in any case, it is recommended to check the permittivity/index values from the Material Explorer before you run a simulation.
You can change the amplitude of the source (to obtain the desired power) from the General tab in the source settings:
You can also verify the change in the power by using the sourcepower script command.
More information on sourcepower can be found on the following page: