Hi there,
I just popped on to say hello casue I saw it was you, Kristen, and thought "Oh how are they doing?' ;-)
Only have a quick second but just wanted to mention Luke also went through a period like this at 18 months. I guess it was separation anxiety. He was always the most independent, non-cuddly baby, and suddenly he wanted to hold hands ALL night long! We ended up bringing an extra mattress in there with him and took turns sleeping in there, and then gradually weaned it. It took a very long time though (maybe 6 weeks ish?!). We have used WI/WO for other sleep probs in the past but this time it seemed that he really needed us there, so that's what we did.
Hope this helps and hope you are all doing well otherwise ;-) x