The group membership acess rights only apply to local connections ie LAN or to users who establish a VPN connection to the server ie they are then part of the LAN.
The only user name and password combination that will work for the ibay is the ibayname and the ibaypassword, NOT the individual user name and passwords.
All (anonmymous) web (http) users will need to logon to the ibay with the same name and password ie ibayname and password. They will only have read permission but not write permission.
If you wish to enforce user acces rights of ibay shares according to group membership and ibay ownership and have read/write permissions, then your external users will need to connect via VPN and (usually) map the ibay to a drive letter eg
net use W: \\serverIP\ibayname
They will automatically have access to the ibay if they already have that permission as per (local) group membership.