The only solution in your case is to use newsfeed. As there's no functionality of liking and commmenting for the wall widget. You will need to implement it on your own or hire a programmer to do that for you.
However there's some flaws in the privacy of the group, like photos from the private group can be seen on user profiles if this newsfeed item has been commented.
Video uploaded to the private group can be seen in the video listings and several other cases, which all have been reported to the devs and is on our roadmap.
I would give it a few weeks unless you need it like right now. Someone could do a plugin for this when they see this post.Is there a way I could make the plugin if I find the proper script?
I can find the files for you but you have to do the work which is why i advised the crash course and the skeleton plugin.
crash course - https://wiki.oxwall.com/dev:crash-course
skeleton plugin - https://developers.oxwall.com/store/item/695