Additional RAM is unlikely to help Kiwi much but might. Watch the Task Manager for a while to see what the peak usage it. Unless Kiwi is queuing messages it doesn't use a lot of RAM, we average less than 250MB at about 500k MPH. It's also a 32bit app so its total usage it limited. More than 4gb would give the OS some space to operate which may improve performance overall.
1.8M MPH is very close to the upper rated limit of the syslog engine(2M MPH) If you are running rules for parsing, writing logs to disk, alerts, etc, those will all reduce that upper limit.
Have you looked at the Kiwi error log(C:\program files (x86)\syslogd\errorlog.txt) to see what is being recorded when the app crashes?