Hello!
Thank you sincerely for sharing my podcast (Fair Folk)! I do love to make it and when strangers appreciate it, it's all the more satisfying.
The Iðunn Society (named after the goddess of eternal youth, appropriately) has a website with lots of information about the rimur tradition, and they are also available by (English-speaking) email. I found a couple of English language articles about rimur on JSTOR, if you have access to that...
Sounds like you have great taste in general. I'll have to check out some other of your suggestions!