Family sharing workaround suggestions?

So, my spouse is the major purchaser of content--all the movies, apple subscription, apple tv subscription, etc., is under his apple ID. Here's the kicker--he has a older computer that he refuses to update the OS for, convinced it will crash his machine. He has no other apple devices. So apparently, his OS is old enough that I can't see his content on my computer or other devices, even though I've accepted the Family Sharing invitation I sent from his machine. Is there any way to work around all this and get access to all his content? I'm kicking myself I didn't insist that we use mine back before we started accumulating all this content, but hindsight is 2020.