I'd bet 50 bucks at least that first picture of the elbow is left over from mudded asbestos fitting. If you wire brush it wet it down first. And yes I would insulate if you have access. You want to keep your steam as steam as long as possible for efficiency.
I think you nailed it - i think one elbow remains - looks like old asbestos or something - I will wear mask - wet it down well and be careful when I clean it up. I will cover these pipes again - I will get some correctly sized fiberglass to cover these. Thanks!