My son was born in March (some years ago), and we definitely turned the heat up (to 68) through the end of that winter (as much for me, up bare-chested in the middle of the night to feed the LO, as for him). I'm pretty sure that by the following winter we just went back to our usual (which is thermostat down to 55 at bedtime, though of course the temperature drops only gradually). We do keep it at 68 when we are awake. We did use the sleep sacks @kkbmustang mentions b/c blankets aren't (or weren't) recommended for little babies sleeping. As we moved toward using blankets, I used knit ones that seemed to allow more air circulation, rather than solid/fabric ones.
As for the NG, I can tell you that 2 years ago our NG company offered to connect our house for free provided we hooked in a NG heater (we accepted). You could check whether there's anything similar in your area, though I'd guess such offers are uncommon I really have no idea.