Hello,
So for other users running into the same issue, use current_user to access suer data.
On the login page, the button should trigger and event. If the Action of 'redirect to URL' is not working as you want, instead set the action to 'Go to App' and from there you can pass in hash params with any data you want to capture from the login app.
These hash params can include the username and password, which can be extracted from their input components with {{ }}