OK - so your exec is running so it does not need ISPF facilities. You are getting slightly different output - the first few fields are ok it goes wrong when you get to jobname. I have never used Rexx to query SDSF so I cannot help. I would check the SDSF manual to see if it says something about differences between executing Rexx execs in foreground and backgroud.
The problem I have is that people can explain things quickly but I can only comprehend slowly.