Definitely if you want a winter range of 100 then a 2015 Leaf will not do. I don't think your experience is abnormal. In winter at speed I was getting more like your 2 miles for 3%. I find that once the GOM is below about 76 then it is not too bad; it is just the high predictions that are a problem. That tells me the original EPA estimates of 73 or 75 are probably right on. Besides which, you probably want to avoid going below 10% unless you know that next charge is right around the corner.
2015 Leaf S. Red. 36960 miles. Great car but traded in for Tesla Model 3 on 12/17/2018.