Old FDM Classic API does not match 1-to-1 to new Jython API, not even the new VB API in FDMEE does.
Being said that, high level solution in FDMEE could be (you would probably know better than me why you want to follow that sequence)
1. Create an event script for Data Load Rule 1 to execute before loading data
- create a temp file to be imported by Data Load Rule 2 (if the source file for DLR1 is valid, then use that)
- execute the Data Load Rule 2 with loaddata.bat using Import only (import will import and validate)
2. Create an event script for Data Load Rule 1 to execute after loading data
- execute the Data Load Rule 2 with loaddata.bat using Export only
You can also do this with batch definitions and one script to set source data for data load rule 2
I hope that helps
The object model is completely different in FDMEE than classic so you are not going to be able to do a direct translation of your current process based on VB scripting into FDMEE using Jython. You will be better served thinking about the original requirement and how you can implement in FDMEE using its new constructs Data Load Rules etc rather than trying to just lift and shift FDM classic scripts which as you have found can be problematic.