I'm going to start by answering your last question first just for fun. In this site, it says that:
Place the pot over a low flame. A low flame increases the brew time, which enhances the flavor. At a later step, you’ll want a slow trickle of espresso instead of a full-force fountain.
You would want a nice, long brew time. The flavor will be enhanced rather than the quick brew time with a large fire. So flavor and brew time can be changed depending on the size of your heat. To answer that question, YES it is a great idea to turn down the heat. EXTRA: The site also shows how to make a nice moka (not spam)! Second, you really answered your last question yourself. Low heat is better than high heat.
Now I'm going to answer your second question. Looks like this site uses Italian pots just like your induction hob. For stovetop pots and not stovepot pots, it says that:
When the water in the tank has been exhausted, that's when you hear the ‘gurgle’ that signifies the drink is ready to pour (approximately 4 to 5 minutes).
Looks like 4 to 5 minutes is just the right time for the coffee to be ready for extraction here. You should know the sound of someone using mouthwash and gurgling. The coffee pot will start to produce that sound when coffee is ready.
Now I will answer your first question. I can't seem to find any significant information on your question, so I'll take a shot at it.
Supposedly, it might be your decision.
Maybe some people like this setting while others like another. I don't know what your standards for a good brew is so I'll just say that you should choose it. Sorry for the lack of information! I hope this answer answered all your questions!