First off, the GRC website is not really to be trusted. "Stealth" ports mean diddly when it comes to someone potentially hacking into your system. And really "stealth" ports are just ports that aren't open. Or even more specifically, that when this program tried to communicate on that port, it was unable to establish a connection. "Closed" ports would have been a much more accurate description, but it doesn't have the same oomph that "stealth" does in people's minds. And the guy behind the GRC website is a very talented marketer, as shown by this little display of psycholinguistics, but a laughing stock of a security expert, as shown by telling people that "stealth" ports are some great thing for security.
That being said, the 64-key passphrase and 32 hexadecimal SSID you keep mentioning makes no sense at all. It sounds like you're mixing and matching a few things from different areas. It's understandable, since even basic IT security can demand a pretty high level of knowledge to really make sense of. It's not something the average person has, or even necessarily should have.
However, if you're using WPA encryption, that's a good thing, and if you've disabled SSID broadcasting, that also is a good thing. I'd add to that MAC Address Filtering if your router supports it. None of those things alone will be enough to secure you, but together, it's less likely anything will happen. Anyone interested in making use of your network will likely move on to a different one that doesn't require as much effort to connect to.
Like I said, it sounds like your garden variety port scan. In a few days it will probably start to subside. Some of it could also be the normal back and forth chatter generated when you load a website or play a game online. It sounds like the router's firewall is doing its job and keeping it out, so there doesn't seem to be any real reason for alarm.