"No password field means I can't set the password for a local db account though."

Do you have Use Database Authentication checked in Site Settings? What Jamie is saying is that checkbox must be checked to use both ldap and database authentication whereas in older versions there was a web.config setting. If it is checked then the password field should be available on ManageUsers.aspx

On the site where the tabs are not working it looks like an unmodified version of artisteer31-green skin, can you copy the latest version of that skin from the /Data/skins folder into /Data/Sites/5/skins and see if that solves it?

If your layout.master file has this:

<portal:ScriptLoader ID="ScriptLoader1" runat="server" IncludeSizzle="true" />

remove the IncludeSizzle="true"

also if it has this:

<portal:SkinFolderScript ID="sfs1" runat="server" ScriptFileName="script.js" AddToCombinedScript="true" />

try setting AddToCombinedScript="false"