What is in the "gum base" of this gum (I've heard that it is plastic free but want to confirm)?

From the FAQ on their site: "Our gum base is composed of resins, waxes, fillers and elastomers, no plastics. The United States Code of Federal Regulations (CFR), Title21, Section 172.615 lists the materials that are approved for use in gum base. There are many different types of gum bases. Exact components are unavailable as these are considered proprietary from our supplier. Xylichew is one of only a few gum brands using a gum base that is totally preservative free. We are a totally preservative free gum / gum base." http://xylichew.com/faq/

What is the gum base made from? Natural or petrol based?

Our gum base is composed of resins, waxes, fillers and elastomers, no plastics. The United States Code of Federal Regulations (CFR), Title21, Section 172.615 lists the materials that are approved for use in gum base. There are many different types of gum bases. Exact components are unavailable as these are considered proprietary from our supplier. Xylichew is one of only a few gum brands using a gum base that is totally preservative free. We are a totally preservative free gum / gum base.

how does this have 1 carb but 0 calories?

Xylitol is a sugar alcohol. As such the human body cannot absorb it so even tho it is technically a carb, it has no nutritive value and hence no calories.