For delta DTP, since you converted from 3.x to 7 process. all request in PSA will be tag as new for DTP and will be sent to DSO, that's why there are more records going to DSO when you execute delta DTP.
For the full load. i'm not sure but maybe the DSO still recognizes the 3.x format where you cannot do full load once you have created init/delta to the DSO.
have you done re-setup of LO Cockpit again in ecc or just migrated the process from 3.x to 7 in BW?