B-747-400 Captain reported a discrepancy with an operational weight restriction due to a MEL; that was not available information to the flight crew but prevented close out information. The crew worked with the dispatcher to discover and correct the minimum fuel loading and comply with the MEL minimum weight requirement.

Narrative

Aircraft X was scheduled ZZZ to ZZZ1. The aircraft had multiple DDG's (Dispatch Deviation Guide)/MEL's; 7 DDG's to be exact. One particular DDG XX-XX-XX-02 (EEC (Electronic Engine Control) System) resulted in a NOGO due to a mistake by our dispatcher. We also had Ballast Fuel of 2401 kilograms When we tried to get FDP (Flight Duty Period) at around XA:45 Z via ACARS it resulted with the correct Remarks: XX-XX-XX-02 and XX-XX-01A; however it also generated LOW GROSS WT/AFT CG COND without Takeoff numbers. It looked very suspicious to me; since we had Ballast fuel with the remark in the Flight Plan for Aircraft CG. I sent an ACARS message at XB:50 Z to our dispatcher and asked him to look in to it. He responded that he will and we received a message from him sometime later to try again. We were busy with multiple MEL's and with Maintenance. At XC:33 Z we requested the FDP again and the result was exactly the same. We tried diligently to find our mistake; read the DDG/MEL again and could not figure out why the ACARS would not produce an FDP. At this point I called the dispatcher and had a long conversation with him; provided him all the pertinent information and asked him as to why we could not get an FDP. After going over everything; he could not figure out why the ACARS did not generate FDP. He than asked me if we had Temporary Repair with the correct Remarks and I told him yes we do. He insisted 5 times over about 10 to 12 minutes that since we had a Temporary Repair and the Remarks we must use it and that it's legal. I in turn insisted for him to find a reason and provide that to me; since I think something is not right here. Finally I told him to get help or call his supervisor. Upon getting help I heard another dispatcher tell him that we must be at the Minimum Gross Weight of 240;000 KG due the requirements by DDG XX-XX-XX-02; we were at Gross Weight of 206;000 KG. That required us to have 82;000 kg of fuel; we were planned at 44;400 kg. Thats when the dispatcher sent us the ARCARS message with the Minimum Weight Requirement; which is NOT available to the crew. Now can anybody imagine if I had listen to him and used a FULL NO DERATE TAKEOFF WITH AFT GROSS WEIGHT CG and an EMPTY Aircraft; what the result would have been?! We would have made the Global News; our family perhaps would be not only grieving our deaths; but also the wrath of the media of us being incompetent aviators.That was very upsetting to us. What was more upsetting and dangerous is that we looked up that DDG/MEL again and again; and it mentions absolutely nothing about the Minimum required Gross Weight for takeoff. I think that is reckless and extremely dangerous. How can we trap this grave mistake without accurate information from our manuals?Suggestions: I know we all make mistakes and I have made them myself. Our dispatcher; upon realizing his mistake was very apologetic and upset. The reason for this Report is to help us all; pilots and dispatchers to become better at what we tasked to do. What I hope the result will be is more training and better manuals for us all to be safe.Thank you very much!