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Some answers:
1. Using FLO_FR is usually not needed. If the demand has a COM_FR specified for it, and the processes producing the demand are at the ANNUAL level, then any input(s) of DAYNITE level commodities to the demand processes will have DAYNITE level flows and will reproduce the load curves defined for the demands. However, if the demand processes are at the DAYNITE level, then you will need to ensure that the load profile for each individual demand process is appropriate, by using either NCAP_AF of FLO_FR for each timeslice.
2. COM_CSTPRD defines a cost per unit of commodity production. For example, if your currency unit is MEUR2010 (millions of 2010 Euros) and your flow unit is PJ, defining COM_CSTPRD(r,y,c,ANNUAL,MEUR2010)=1.7 means a cost of 1.7 EUR2010 per GJ.