Would protopic (tacrolimus ointment) be good for poison ivy?

No. Protopic is great for chronic treatment of eczema, but poison ivy needs a much more potent anti-inflammatory medication. The inflammation due to poison ivy is so severe that even the high-potency topical steroids often aren't enough; oral steroids are usually required.
No. Tacrolimus, quite frankly, isn't much good for anything. It was billed as a replacement for steroid creams when it came out, but it doesn't work nearly as well, if at all, in most cases. The inflammatory reaction is usually pretty significant in poison ivy; except in the very mildest cases, tacrolimus won't even make a dent.