Something like that but you could be more clever than that depending on which language you want to write the script action in and how clever you want to get. Other options are included at Design Pattern: Encoding and Accessing Values in Rules though note that’s an old tutorial I’ve not updated yet and not all those options are available in the UI.
I would probably use the Item name approach or the Item Metadata approach.
What I meant was having 50 rules would require a tiny, perhaps unmeasurable, more RAM than having just the one rule. In other words, there is no meaningful performance impact to having the 50 rules.
The default Xms and Xmx settings are fine. And I think the Xmx setting causes Java to go out and grab that amount of memory when it starts up.