Does that mean I'm bound to the preset level on which my Switch is tied? IE: My switch is on house code "D". Does that mean I can only have 16% or 68% ?
No, you are not "bound to the preset level on which my Switch is tied." Although most commands must use the same house code as the module you are controlling, the PresetDim commands do not. That is one reason why X10 never implemented the PresetDim command in any of their modules and developed an "Extended Dim" command instead (used by their 2-way lamp module).
Is there a way to acccess to other values with the "sendplc" command? Do I need to use the "sendrawplc"
Yes. You need to send two separate commands though (one for the address and one for the command). For example if your module is set to address D5, and you wanted to dim it to 52%, you would send the following commands:
sendplc D5
sendplc M PresetDim2Kind of strange I know, but that is how it works.