StackedColumn3D does show the totals and the values for individual bar elements by default. Do you have any options set which would remove the totals? Alternatively, if you use PNG charts and the axis labels also missing, then you should check the ChartDir font installation in the server.
If you run the updater, you can control the gaps between bars with:
select 'dbr.chart.options', 'bargap', 0.2;
where the 0.2 is percentage of the gap (0-1), negative for overlap.
The width_per_item-option is meant to be used if you have dynamic number of columns / bars and set the x or y size of the chart to be 'auto'. In that case the chart resizes itself based on number of columns / bars is to be shown.