Hi Elisavet,
The property that you need to modify to set the .DAT file being used by the Source File is FileName1. If you look at Example 21 in our sample code files, you'll see it being used to set 'RAYFILE_LB_T67C_100K_190608_ZEMAX.DAT' as the source data:
#! [e21s03_py]
# Set 1st object as a Source File
Object_1 = TheNCE.GetObjectAt(1)
Typeset_SourceFile = Object_1.GetObjectTypeSettings(ZOSAPI.Editors.NCE.ObjectType.SourceFile)
Typeset_SourceFile.FileName1 = 'RAYFILE_LB_T67C_100K_190608_ZEMAX.DAT'
Object_1.ChangeType(Typeset_SourceFile)
Object_1.GetObjectCell(ZOSAPI.Editors.NCE.ObjectColumn.Par1).IntegerValue = 5
Object_1.GetObjectCell(ZOSAPI.Editors.NCE.ObjectColumn.Par2).IntegerValue = 1000
Object_1.GetObjectCell(ZOSAPI.Editors.NCE.ObjectColumn.Par3).DoubleValue = 2.485572
Object_1.GetObjectCell(ZOSAPI.Editors.NCE.ObjectColumn.Par8).DoubleValue = 0.47
Object_1.GetObjectCell(ZOSAPI.Editors.NCE.ObjectColumn.Par9).DoubleValue = 0.47
#! [e21s03_py]
As for the conversion from text to binary data, I don't think we have any native tool that performs this action. I think it would have to be something that you create yourself -- for example, we do have a related article which covers going from binary to text formats. You can read that here, and it comes with a sample code and executable file to perform the conversion.
Lastly, we do not currently have a way to save images from layout and analysis windows from the API. What we do recommend, if possible, is to leverage something like the EXPORTJPG/EXPORTBMP ZPL keywords, though this would mean writing a macro rather than working within the API.
Please let us know if you have any more questions here!
~ Angel