I think DotNetNuke sounds like it will be a great solution for what you are looking for.  You have a whole lot of stuff in that block of text there, but I will try and address it:

Independent membership is not a problem.  The society can have its own portal and each constituent club could have its own portal.

1) Access control is good.  You can create roles, assign users to those roles and configure what pages and even specific modules those roles have access to, on a per portal basis.

2) I would recommend the DnnForge News Articles module from Scott McCulloch (www.ventrian.com).  A basic $20 subscription will get you access to all his modules.  It will provide the categorization and control of articles you are looking for.

3) The ability for users to create their own home pages / about me pages is slightly more complicated.  You might allow each member to create their own portal, but I would recommend sticking with the about me page idea.  For this, I would suggest the UCanUse User Attributes module (www.ucanuse.com).  This module allows you to fully customize the registration process and what information is collected, but also has a 'view' mode that allows you to display a customized view (about me page) of information in a read only format.

4) As far as Image Galleries go, I like the DnnForge Simple Gallery module the best, which you will gain access to via the same subscription mentioned above.  As far as forums go, its a toss up.  The core forums are decent, and free.  I think the Active Forums from activemodules.com is the best forum out there though.  That goes for somewhere around $60.  All should be searchable via the standard search box.

5) The Free Text Box (FTB) editor that comes standard with DNN should work just fine for you.  Alternate text editors you could check out if you are not satisfied with that would be the CuteSoft CuteEditor and the Telerik rad editor.

So pretty much, DotNetNuke offers everything you are asking for, and a whole lot more.