Well, because i'm using an older version, i really don't feel like checking the files out, but from a really quick glance at it, you could replace the series of repeated events with a function call (a separate object you have to add).
Furthermore, you could nest the 201 and 202 events (drag the one below slightly below the 201, when it becomes a sub-event, delete the common conditions). This could probably be done in other places too.
Sorry if this isn't much help, buddy... :/
Not related exactly to your inventory system, but you really should disable the retina display option - it's a performance hog.
Just check the results in the performance benchmark that was done for C2 a while ago. The difference was 20x in some cases.