RE: #1. I'm at a complete loss why an expat staying by reason of marriage has to only have 400k in the bank, when he has a wife and quite possibly kids to provide for, and why an expat on a retirement visa/extensions has to have 800k in the bank, when he/she is more than likely single with only himself/herself to provide for. I fail to see any logic in this.
Agreed - no logic - just a simplistic requirement to try to guarantee long stay visa holders have substantial financial means in country.
Neither the 400K or 800K (which started out as an alternative to claiming minimum monthly income) will ever get spent because to do so will invalidate your long stay visa immediately and that would be unfortunate to put it mildly.