How can I change Finder's "Name" column width in "List" view in El Capitan?
Actually, the solution in your linked question still works as of 10.11.6 - I think your issue is you are confusing Column View &amp; List View... based on your stating '"Name" column', which column view doesn't have. 

For List View, just drag the column header divider.
To make it default,  Cmd ⌘   J  &amp; Click 'Use as Defaults'.

I am uncertain as to whether that will override any existing ._DS_Store setting for other windows - you may need to clear them if you want to start afresh with your new defaults.