When you use a data table variable it wont get the values because your using, well, a variable. Its dynamic. You have to select the data table you want manually in the GetDataTableRow or column nodes. If you want each npc to have a different data table then you can use an enum as your variable to decide between which data tables you want to use.
This will work for now, but I will warn that having a separate table for every NPC is not ideal. Ideally you will have the data for every NPC stored in the same table, or split across a few tables.