aren't I supposed to have a unique forum for each group

Yes, GJ will create a forum category for GJ Categories, then in those forum categories for GJ Categories it will create GJ Group categories. Example as follows.

Groups
- Category 001
- - Group 001
- - Group 002

Confirmed and tested as working on GJ 2.4 and latest release of Kunena.

Right now in my main forum, all 5 groups postings are also shown there and and all recent postings for all 5 of them are all jumbled together in the main forum's recent postings

Of course the posts will show under Recent Posts. It's not duplicate posting anything. Recent Posts does exactly what its name implies. It shows the most recent posts. Recent posts doesn't show recent posts from a specific category, it shows them from all categories ordered by date (so they'll look jumbled). GJ uses Kunenas access API to determine if a user has read access or not.

GJ can not control access to Kunena however if you do not have Kunena setup properly for CB. Please navigate to Kunena > Forum Configuration > Integration and set the below accordingly.

Avatars: Community Builder
Profiles and User List: Community Builder
Login and Registration: Community Builder
Private Messaging: Community Builder
Activity Notifications: Community Builder
Access Control: Community Builder

If issue persists please PM backend super administrator login credentials and will take a look.

I've reviewed your install and it's working as intended. All of your GJ category and group forums are within the Groups category. For example on that main forum page under "Groups" is your only GJ category "Radio Groups" then inside of that is all of your GJ groups forums.

The problem you're having is you've set the first page Kunena to open is "Recent Topics", which of course is going to show GJs posts. However, people can only see posts from the GJ groups if they actually have access. Currently with GJ 2.4 there is a bug with that access (due to "Public" parameter for group forum configuration) that is resolved with next release.

You could also be subject to the below bug if you allow public posting.

forge.joomlapolis.com/issues/2844

Will this issue also resolve it for "registered" users being able to post in group forums via the main forum?

Yes, GJ 2.5 will solve this. It's a permission bug.

Any idea when this issue/update will be put into place?

Before end of this year.

Is there anyway for the "group" forums and groups posts to not be integrated into the main forum as well? I would really like for each group to have a forum allocated/dedicated just for them and not merged with my regular forum.

Again, group posts are not in your main forum. Your first page is "Recent Topics" and it shows posts from all categories as long as the user has access to that category. Group posts are inside of their own group categories. I've explained this numerous times and do not know what else to tell you. Change your first page from Recent Topics to Categories and you'll see the category list. Your Kunena menu also isn't working so you can't even click to change the view. Please take your issue to Kunena as again it's nothing to do with GJ. You can view your forum layout by navigating to Kunena backend Category Manager.