You can use the map() function to get values out of your aggregated arrays. There is tons on that in the community and the help docs, but can I recommend you start with the Make for Make Newbies video series I put together - it will help you tremendously to understand how to access the necessary pieces of data in this scenario and future scenarios.
You may not even need the iterator/aggregator if you can access the Custom Field Values collection. IF you can share what that specific collection looks like from your output bundles we can work on figuring out how to reference various keys in that collection and their respective values.
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Alex Sirota
Director of NewPath Consulting - we are 
Make Heroes! 
Check out my series of videos and scenario walkthroughs for Make Newbies