There is EVCC.io which greatly extends the capabilities of a Victron charging station (planned charges and such). Although your consumption forecast will still get poisoned by the irregular consumption.
The problems you are describing are widely voiced on the forum. There is a DESS node red implementation that would allow you to steer the behavior of the battery, but it will be phased out. I have found a custom integration by ikke050, but I have not used it. My wish for a more flexible system pushed me to develop my own DESS. But that is still far from finished. I wish I could give a better answer, but the current state of DESS just does not allow you to bring your own consumption forecasts.
EDIT: I also found that Victron is using different models for ev forecasting