This isn't going to be good news for you, I'm afraid. The 'health bar,' if you mean the little bars next to the charge bars, indicates remaining battery capacity, and the bars don't come back, except sometimes briefly as they are being lost. The first generation battery packs degrade too quickly over time, and far too quickly when they get hot in Summer, so this isn't your fault, but you have lost roughly 30-40% of your original capacity. There is a court-mandated capacity warranty, but it is for 5 years or 60,000 miles after the car's in-service date, and yours has likely expired. Even if it hasn't yet, you have to have 8 bars to get a new pack, not 10. Recount the bars carefully, including the two red ones at the bottom.
Now, as to Winter range: I suggest you block your car's grille, and inflate the tires to 40psi. You car lacks a heater Off switch, but that isn't an issue in the dead of Winter for most people. I suggest you lower the heater blower speed to the lowest or next lowest setting, and use a 12 volt heated fleece throw to increase your comfort. I'll repost my Tips & Tricks topic as well. Take a look at it.http://www.mynissanleaf.com/viewtopic.php?f=38&t=23297