Hello,
Regarding point 1,
Yes you need to have intermediate nodes for proper connectivity . Yes the analysis and design will be correct .
Regarding point 2 ,
I am not sure what exactly you mean by the PV weight , but if you don’t want to model the PV in Staad , then you may put the PV weight as udl load on the aluminum rail .
Also, I would recommend you to use the Bentley Technical Support and quick response to all your queries . You may create a Service Ticket and Technical Support Engineer will get back to you .