Welcome. First, ignore the estimated miles of range. The algorithm that the car uses to estimate range is too primitive to be useful. It looks at just the power consumption of the last few minutes, and estimates range based on that consumption. Since most people are gentle with the accelerator pedal as they park the car, the estimate at the beginning of a trip is especially wrong - at least for most people.
What you need to do is estimate the true range of the car with you driving it. The dash display needs to be set to display the state of charge (SOC) as a percentage. Note the state of charge, and the odometer reading (you can also reset the trip odometer. Then, drive the car as you normally do, until you have used either 10% of the charge (i.e from 55% to 45%) or, for better accuracy, 20% of it. Then multiply the number of miles you have traveled to use that percentage by either 10 or 5, depending on which percentage of charge you used. This is close to the true range of the car.
Now, which model 2015 Leaf is this? If it's an SV or SL, then it has a heat pump that will extend the range in moderately cold weather (down to roughly 30F), along with seat warmers and a steering wheel warmer. If it is an S, then it has only resistance heat, which drains charge quickly when used, in all temperatures. Also, what is your climate like? Hot? Temperate? Cold? That will greatly affect the Winter range, and if it's Hot, then it will also affect the battery life.
That slack in the drivetrain is very likely play in the axles due to improper torquing at the factory. There is a Technical Service Bulletin on this, and a dealer should fix it for free.