Enable GC logging, once the Eclipse crashes again, you will see the cause of the problem, the logs will show you the size of PermGen.
GC logging :-XX:+UnlockDiagnosticVMOptions -XX:+LogVMOutput -XX:LogFile=jvm.log -XX:+HeapDumpOnOutOfMemoryError -Xloggc:gc.log -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -showversion
Considering the PermGen being part of the Heap or not, this actually depends on the version of the Hotspot you are running. The GC algorithm controls the size of the PermGen, so even though you set MAX=1GB, it may never grow that big and you can still get OOM because of some other issue.