1. First for your situational awareness, note options are not needed on IDIQs. Due to the nature of IDIQs, the government only needs to fulfill the minimum requirement as referenced in FAR 16.504(a)(1). Beyond the minimum, then task orders can be issued as needed, but the government is not required to issue them. 

To answer your question, the FMR does not contradict the DFARS. Finance can provide funding by fiscal year, or cross fiscal years and provide the whole amount up to 12 months of service. The task order would be properly funded either way, so it can be issued. Just ensure the whole period of performance is funded either on a fiscal year basis or crossing fiscal years. 

2. The prescription for the DFARS clause says to add it "in solicitations and resultant incrementally funded fixed-price contracts." As such, if it is planned to have incremental funding for the IDIQ, that clause should be added in the base IDIQ. 

3. If the contractor were to perform on a contract without funding, that would be an Anti-Deficiency Act (ADA) violation. So in other words, contractors performing without funding is not legal as the ADA is a statutory requirement. The only solution is if there is not funding, then the contractor cannot perform. If that is acceptable to your requiring activity, then task orders can be issued for shorter periods before and after the period that would not have funding.