Definitely get a workers compensation attorney. If indeed the injury is legitimate, the fact that your fiancee didn't follow doctor's orders doesn't mean he is defrauding the workers comp system or should be suspended. The fact is, however, employees with injuries are often fired, so my advice would be for your fiancee to get the treatment he needs, get better, and look for another job, since it seems his credibility with his current employer is ruined.
You should always retain the services of a workers' compensation attorney. Since most workers' compensation cases are done on contingency, it does not cost you anything.
Remember your employer has the workers compensation carrier, nurse case managers, investigators, adjusters, supervisors, in house counsel and maybe even the physicians looking out for their interests. Even with an attorney the deck is stacked in favor of the employer/carrier and their unlimited resources.
Yes, in all reasonable probability, the services of a skilled workers' compensation in your area will be well worth it to your fiancée. In California, most attorney's for injured workers' limit their fee request to 15% of the settlement approved by a Workers' Compensation Administrative Law Judge, and all fee requests must be approved by a judge before fees are paid to an attorney.
In your fiancee's situation, an attorney is especially needed as his matter is headed toward trial as the defendant has films of him apparently performing activities that are beyond his work restrictions. If he told a doctor that he cannot perform a certain activity such as lifting objects over a certain weight, and the films show him performing those activities, his credibility is at issue. This is a facts and circumstances analysis and a skilled trial attorney will be needed to cross-examine the investigator who will testify at trial when the investigator shows the films to the court. Also, doctors will review the films and match the activities films to the applicant's claim of restrictions on his activities.
Although workers' compensation was originally designed for persons to navigate the system without the need for an attorney, please reread the excellent commentary from David Alan Karas, above this response: The insurance carrier or employer has a potentially limitless well of resources (investigators, adjusters, attorneys, in-house doctors and nurse case managers, etc.) to round-table with and decide how to best fight the claim. A skilled attorney is the only resource your fiancée will have to counter that legal firepower. Believe me. I have about fifteen years of experience representing defendants in workers' compensation in addition to the nine years that I represented injured workers.