Hi Galen,
There is definitely something unusual. The default setting should be more than adequate based on basic debug that you described. There are some views that do use significantly more memory and increasing heap size can help, if multiple instances of those editors are opened. I had a few basic debug views opened, about 10 editor windows and an active debug session and my heap usage was about 120MB. The limit is currently set at 384 (5.3 and 5.5 have the same setting). Could you open Window->Preferences and then go to General category. On the right hand pane there should be a checkbox titled "Show heap status". Please enable it, it should show current heap utilization in bottom right hand corner of main CCS window. I would expect those JVM low messages to appear around the 360-370MB mark. Is there any kind of specific views, actions or commands that seem to trigger abnormal growth in heap utilization?
Martin