All you need is proof of onward travel, does not need to be a return ticket. So just book the flight to the next country you plan to visit or use one of the "onward travel" sites that reserves a ticket for a set number of days and works as proof. Costs something like $10-15
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.