A - that symphony of sorcery method for money is just one way. Others include the kab kannon. Scan up your kab kannon, pet him for 10lp (or food) buy dark firaga. release him. scan kab kannon, get 10lp sell dark firaga. some others include buying slot edges from the medal shop and selling them off for 600 gil a pop i believe. you can get 2 or 3 per match in the later matches. I personally have enver had a problem with moeny though. i had over 300k at one stage after selling off all my dream pieces after making everything S-rank. I would probably suggest that the increased drop rate forecast + twtnw would be the most lucrative with money, given how much you can sell off some dream pieces for. maybe. that SoS method only yields like 30k an hour. which really isnt much.
B - for experience, I personally find just making runs through TWTNW to be the best. (and i have both characters at 99, and a level 99 skelter and Ryu <3). with riku, just start at the back just before his ABCN boss fight, and retread to the beginning. (its faster because you're going down instead and not up)then exit to map and reenter from the back. My deck is megaflare x2 (the one from ryu dragon, and the one from s-ranking TWTNW dive) meteor, Thundaga/balloonga and a drop-me-not. (dropping is annoying if you're grinding one character so...) that said, replace thundaga/balloonga with sacrifice to keep yourself in the exp boost range easier, and turn off treasure magnets. Grinding really isn't a problem in this game.
For sora, I make a trip through the contorted city (? the first area) until i hit the second area, then turn around and back track through the first area, then exit to the world map and reenter. i think my deck had 2 megaflares and faith.
that said, there is no reason to grind yet if you havent done all you portals and whatever else you still have left.
C - sephy, why are you using food to change dispositions when it so VERY easy to change disposition via petting, to exactly what you want? heres some self advertising when it comes to DE's,
Kingdom Hearts 3D: Dream Drop Distance FAQs, Walkthroughs, and Guides for 3DS - GameFAQs
Again though, no need to 'grind' until you have everything else you want to get first that requires fighting.