For the login page failing login, you have the wrong bindings in the authenticate user server behavior. you are using recordset bindings where you should be using the bindings for the login form.
edit the authenticate user server behavior, on the database tab, edit the bindings used for the username and password columns to use the username and password form elements rather than using the bindings from the interprimus recordset.
for the error you get on linking from a different page, I'll need to troubleshoot directly, see the private message section.