But most of us learned early on to draw a line in the sand, even if it means walking away from a job.
The original poster signed a contract. He gave his word. A man would pay up.
The waisting of bandwidth aside, it seems plausible that the original poster is in essence drawing the proverbial line in the sand and ultimately walking away from a job because of it.
Obviously, we don't know to what degree any of the conditions the poster explains exist. But as you stated "most of us have been there and done that". I feel certain there are employers in all industries that would do this; I know there are in aviation. All of your analogies withstanding, certainly no PIC (or SIC, FEX, FA, etc.) should violate a regulation or compromise safety at the demand of the employer, but we know some employers will do just that, knowingly and unknowingly, by both direct and indirect methods in a sometimes seemingly blind pursuit of revenue.
Yes, he signed a contract (of which we arguably don't know the legal merit or wording), but I'm sure in his opinion, understanding, and intent in signing it was that it applied to a specific job function, stated compensation, promised work conditions, etc. If those change in the manner the poster explained then the faith of the contract is violated, i.e broken and the employer has not held up his obligations in the contract.
FWIW, I have refused to sign training contracts, even with employers that "require" them for many of the issues discussed in this thread. However, I have experienced issues with employers that, had I signed one, certainly would have justified voiding the contract and I would have done so with good conscience. Yes, I consider myself a highly ethical person and greatly value my word, but the simple fact is the some people (managers, employers, and employees alike) do not and will lie to you. I think it is great advice to have conditions specifically addressed in a contract, but just because they are not doesn't remove both parties obligations in a contract... ethically speaking.