I've experienced this too when my sister invited me to get-togethers with her college friends (she was also in the arts, in a very tight-knit cohort). The main strategy I used to re-insert myself into the conversation was indeed asking questions. You mentioned that you did ask questions, but usually to clarify. So I hope this doesn't repeat too much of what you've already tried.
There's two main drawbacks to clarifying questions:
They're not very interactive - the person talking can just give a quick answer ("yep, that's the guy") and carry on, like you describe.
While they sometimes work as a polite way to signal "hey, outsider here", the group might not pick up the hint. Even then, it's easy for conversation slide back into the same topics anyways simply because they're the majority. (That happened at one event I attended, even after someone said "Hey guys, Em is being left out, let's talk about something else".)
Instead, identify points that you do have some interest in, and ask open-ended questions to prompt them to talk about that. Finding common ground is a good principle for conversations in general! For instance, you might not care much about Some Theater Show that they were in, but maybe you're curious about set design or how they change costumes so quickly. (Based on my experience with friends in college musicals - even if you don't think they were directly involved, they probably still know something about it.)
Even if you don't really know anything about what they're discussing, it can be a very effective conversation starter to make a guess - "I think I heard something about such-and-such, is that really true?" - and they'll be happy to correct you if you're wrong (see also: Cunningham's Law). Or, pick something that's common to most college experiences and comes with a story you might be able to relate to - times you stayed up too late, worst classes, favorite professors, etc.
Asking these types of questions usually resulted in a back-and-forth exchange - they answer, I follow up, etc. It lets you steer the conversation a bit, but still within the topic they're already discussing, so it's more likely to "stick" (and hopefully is more interesting for you to listen to).
For events where you know in advance who will be there, you can also try to come up with some questions beforehand. (A strategy used by Churchill1: "I'm just preparing my impromptu remarks.") I definitely encourage enlisting your wife for help. She knows these people best, and can help steer ("Oh that reminds me, Rainbacon likes photography, tell him about...") or facilitate introductions to new friends ("This is Anna, she likes cats too!").
Another / complementary strategy is to take a playful approach. Since siblings tend to tease each other, I used that as a way to interject too. You could try something similar with your wife - "Oh really, I heard you all went there for spring break, but I didn't know that! What else is she keeping from me??" My sister's friends were all too happy to share more, and I felt more engaged, because 1) they were watching for my reaction, and 2) it gave me an opening to share stories about our shared history ("That doesn't surprise me, did you know this one time she..."). Of course - this depends on the context, and whether your wife is comfortable with it :)
Finally - if questions don't work, distractions might. Even when I couldn't contribute to that part of the conversation, we still had fun playing board games together. It didn't stop their college reminiscing, but it did guarantee we had a common topic (the game) to chat about while playing.
And.. if I can give some more intrapersonal advice -- manage your expectations. I was more satisfied when I expected to be outside my comfort zone and treated it like "how well can I fake having social skills", than when I hoped someone would take an interest in my college/career path and was disappointed. It also helped me to have a temporary "escape hatch" when I felt too lost and awkward - maybe you could arrange something with your wife beforehand, like excusing yourself to go clean up the dishes while they watch their recording.
1Well, maybe - if anyone has the original source, please drop a link!