Insufficient ram issue is common in Symbian platform.You can try to uninstall apps or flash with custom rom for some performance gain.But there is no permanent solution.
Symbian's build in browser is crap.Opera Mini is goos alternative since it will sort of compress of the data before the browser display content in your phone.But like most of the mobile browser it will only open mobile sites properly.
As far as I know for Nokia there are only Firefox(fennec) & microB browsers capable of browsing sites as well as desktop browsers.Unfortunately both is exclusive for N900 which is running entirely different OS(maemo).