Hi Edi,
For point no 2,the below DS may be useful,
2LIS_11_VAITM
2LIS_12_*ITM
and
2LIS_13_VDITM
Modelling needs to be done for this ....Combination of the Three DS into one DSO and then to cube.
For point no 3,the below discussion may b useful.
http://scn.sap.com/thread/2012519
For Point no 5,
you can check the AR flow 0FI_AR_04 with document type filter as Cash .
Rgds
SVU