Sorry! I didn't see your first post until today.
You have a lot of pork belly. If it were me, I would take the belly and rinse it off; since you only were able to place about half the mixture into the bag with the belly. I would divide it into 1 to 2 pound sections. The smaller sections are easier to work with. If you don't currently have all the supplies to cure the bellies again, then freeze the bellies for now, and purchase the supplies you need. Those smaller sections will fit easily in 2 gallon sealable bags or maybe even a one gallon bag.
Go to the link below, and read the information about Equilibrium Curing. Then go to the Digging Farms calculator. Since you already partially cured the belly, in the calculator separately add the weight of each belly section, change the percentage of Salt to 1.5% (or leave it at 2%), change the Parts Per Million (PPM) to 100. Changing the PPM to 100 will keep you in the safe zone for the maximum amount of nitrites. As long as the meat has at least 40 PPM, your meat is protected from bacteria that can cause botulism. Since you are adding brown sugar, and other sweeteners you can ignore the Sugar section.
Equilibrium CuringCure CalculatorAnother thing you can do is look up recipes for fresh pork belly. I have hot smoke fresh pork belly in the Bradley for a couple of hours, then finished it in a hot oven or over a grill. Do a search for grilled fresh pork belly. It's a rich meal, but very good; though I don't think you would want to turn all 6 pounds of belly into grilled fresh belly. Just keep in mind that you may want to reduce the salt in the recipe.