You don't HAVE to, but if you don't then you won't be getting stamped in for 60 days using the visa. You'll only get stamped in for 30 days on visa exemption.
you'll have to ask your immigration office then or update your post to let others know which one he will be using. I think others are answering assuming it was for retirement which has to be from international transfer. I Don't believe that's the case for the marriage visa at most offices.
I think it depends on what the reason for the non-o is and what immigration office he will be using. Marriage, retirement, etc as there are different requirements for different reasons as well as between different immigration offices.
Becasue its really not that hard if you have the correct documents. Sometimes those requirements do change, but not nearly as much as some claim. If you get an updated list prior to going its no problem even if they did.
the official requirement is 400k for two months. You're also not required to ALSO show 40k per month. It's an either or thing. So that is definitely not normal.
For the initial 3 month non-o the 400k does not need to be seasoned at most offices I believe. It simply needs to be in the bank on the day you apply. The seasoning is for the 1 year extension. So you may want to check with the immigration office that serves your area. You may be able to avoid having to leave the country.