I have all the registration redirects pointing to the forum page of my website:
However after a new user resets their password, they still see the default wordpress login screen. If they login there, it results in total confusion. I want them to login in on the forum page so that they end up in the forum and not in a wordpress installation. How can I accomplish this?
If I recall correctly this is probably historic. I believe that when we did the work on the redirects, WordPress had no facility to override the password reset form so we were unable to include it. In all probability that has changed and I admit - we have not looked into it.
Best I can do is add it to the list for a future development. In the meantime you could take a look for a WP plugin that will do this for you. I can't recommend one but there certainly used to be (and I feel sure probably still are) several that could take over the registration/login/reset processes completely and redirect to a page of your choice...
This works very well and has additional features
“I must stop him from being one of those who call themselves good because they have no claws.” ― Irvin D. Yalom, When Nietzsche Wept