Mr. Krabs would probably be thinking about how this could be good for business. He might see it as an opportunity to create a new tourist attraction. Patrick would be really happy for Spongebob at first, but then he might get a bit jealous because he doesn't want to lose his best friend. Squidward would be extremely annoyed by all the commotion and the fact that he has to be part of the wedding in some way.
No. The original Spongebob series is all about fun, friendship and adventures in Bikini Bottom. The 'Spongebob real story' is a completely different and often very dark and inappropriate take that has nothing to do with the original positive nature of the show.
We don't have enough information to know how SpongeBob reacts. He could be really excited and ask for more details, or he could be so tired that he falls asleep right away.
A new character, like a traveling musician fish. Spongebob is always open to new things and experiences, and a music - loving fish could charm him with her melodies. She could perform at the Krusty Krab and Spongebob would be entranced by her talent.
He might be really confused at first. Spongebob is often naive, so he may not immediately understand why everyone is angry. He could just keep smiling and asking what's wrong in his innocent way.