The first error code does mention that "if the connection continues to fail, this Hotspot may have their router set up in a manner that is not compatible with the system. We recommend trying a different location."
So perhaps try connecting your 3DS at a friend or other family member's home and their wireless router to see if you still have the same problems or not.
Then if you can connect, you may need to see if you can change the way you have setup your computer Hotspot, or you might need to use a wireless router instead.