It sounds to me like BrE, but to my American ears, I would assume it means to get into bed. We have an idiom "To hit the sack", which means to go to sleep.

I would use it to describe platonic friends, since new lovers are supposed to spend all their time together...it isn't unusual.

Chili is a kind of stew, spicy with pinto beans and beef. I voted... This is a reference to the Iraq war. One American politician was trying to appease both the pro-war and anti-war crowd by saying "I voted for the war before I voted against

At a "health food store". You won't find prescription drugs. Just vitamins and herbs. (Maybe some cold and flu remedies like NyQuil.) For pharmaceuticals, one would go to a pharmacy, or a drug store.

Imbue looks fine to me. I would expect "a hatred" rather than just "hatred". Looks fine.

Try: I was halfway home. I was halfway to work. I was almost/nearly home. Your sentences work, but they aren't something I would expect to hear.

A gas main is a distribution point for natural gas (methane). Highways have markers, usually every mile, so yes, the 18th mile.

And to add insult to injury, (even worse?) it all went down at tonight's tribute to romantic bliss. There was a wedding. Could she mean that? "Add insult to injury": to hurt someone (physically) and then to insult them. Also, kick

T-minus is a countdown. So there's exactly 3 hours until D-Day. One hears T-minus during NASA launches.

Close, sounds more like she doesn't want love. (Or she's denying any feelings she might have for someone...)