Your .asc file didn't resolve to a functional circuit as a download, but I did get the jist of your request. I constructed a very simplified circuit, and have attached it below as an example of how to step the frequency of a source.
Note the structure of the .step spice command utilizing the parameter and LIST functions along with the return to original state (lower than original state works too).
EDIT: Or one can string it out to a limit using the proper/desired increments as shown in the second thumb.
I have been building an engine speed controller and I have had to build it in pieces for spice, when I run the two pieces by them selves, they work great, but when I join them, I get a time step error. Can someone give me some help. The attached .asc works until I connect the wires to the left. I still need to add op-amp and FETs to drive some valves to the design, but I'm hung up with the error.
Thanks,
kinarfi
Took a look at the yahoo's spice group and the first line said something about fet switches and op-amps and to much capacitance of the fet and that it causes oscillation and suggested the cure was to series a 10 or 100 ohm resistor, tried it and it cured my problem also.