If you have 2 componants such as ART plus FRT iirc the restrictions of ART will apply to ART and the FTR restrictions to FRT

If ART allows stopover in DXB only then you can stop in DXB only on the A direction
If FRT allows unlimited stopovers then you can stop wherever u like in the F direction

I have also found that the online booking tool has issue handling stopover rules and you may find that phoning and speaking to an agent and explaining the situation can deal with issue