OP:

It would be productive for the conversation if you described in detail (it doesn't have to be an essay) what you average day consists of. Do you do anything other than act as SIC on the PA-31? (PIC on something else?)

What, EXACTLY, are they making you do? Although JB "tone" may be rather confrontational, I believe he is asking some of the right questions.

When you say "I do, in fact, operate the aircraft in the right seat. I seem to be given full SIC responsibilities"; are you saying you manipulate flight controls? Do you TOUCH ANYTHING? Do you preflight, postflight the aircraft? Do you handle the radios?

The FAA has recently changed its policy regarding enforcement. If they are truly encouraging, convincing, coercing, etc; you to break the law, then you really do need to go to the FAA about it, they're not going to throw the book at you.