While SharePoint might not be the perfect solution for storing passwords, it is certainly possible to do this in a custom list (like managing any other info). 

 - M: break role inheritance on list/site, remove unwanted
   readers/contributors/owners and give security group containing
   Developers read permissions 
 - S: give selected developers (or security
   group containing these) contributor access 
 - C: create a custom
   permission level "Add only" that gives access to add but not edit and
   assign this to specific users or a security group (this has been
   asked
   [before](http://sharepoint.stackexchange.com/questions/32275/allow-users-to-submit-items-to-a-library-but-not-edit-or-delete))
   
 - W1: Not entirely sure what you mean, but if this means that some list
   items should have special read permissions, just break role   
   inheritance on them and assign special read/edit permissions.
 - W2: In SPOL 2013 you have access to lists using REST. You could pass 
   [this][1] link to your developers.

  [1]: http://msdn.microsoft.com/en-us/library/fp142380.aspx