You're vaping at too low of a power and gunking up your coils because you aren't converting all of the liquid into vapor. Instead, you're converting some of the liquid into a syrup type goo that clogs up your wicks and gets burnt and nasty tasting. It also reduces the air flow so your draw will get tighter with time.
The Nautilus BVC coils really like to be run at high watts, especially with 50% of more PG juices. I run a 50/50 mix at 19 watts and my coils last me more than a month. Don't be afraid to crank up the wattage, but also select a larger air hole when you do. I do mouth to lung hits with mine set on the 2nd largest air hole and it works great.
And as for quitting the smokes, I spent several months vaping and smoking. I didn't stop smoking until I switched away from tobacco flavors entirely. Once I quit using tobacco flavors and switched to mints and menthol flavors I quite smoking within the week. Not because I dedicated myself to quitting smoking, but simply because I found that I preferred the flavor of vaping more. I walked around with a half pack of cigarettes for almost a month "just in case". Once in a while I would take one out, take a couple of puffs, and put the cigarette out because it just tasted nasty.