Indie and I have to ride a few miles of country road (notorious for people flying by as fast as they can, as we are between two highways) to get to our trails, and it does take quite a bit of work to get to the point where you can feel safe riding the entire way. 3 years of riding the same road, and there is still some idiot in a car that will either intentionally try to hit you, honk their horn at you, or spook the horse; you MUST be prepared for that.
As for the horse spooking, put on some tennis shoes and don't be afraid to get down and walk the horse in areas that spook him, give him time to figure it out, and take control as his leader with confidence and it will let him know its okay. Do not however let him train you to get off everytime he spooks... figure out what it is exactly that spooks him (for Indie it's trash bags on the road LOL), and maybe get off ahead of time and walk him past these spooky things... then get on and ride past. This way he does not start figuring that every time he spooks= you get off and thus give him less work. Horses sure are smart about figuring those sorts of things out.
Hopefully you have plenty of shoulder space that this is possible, if not... then I'd suggest finding a different way around. There are very few situations where I will ride directly on the road because there is no space off to the side to comfortably fit the horse and I... again, idiots on the road are intentionally dangerous, or more often just ignorant of riders and our needs.
Keep a cell phone on your person at all times, not in a saddle bag. If the horse runs off and your on the ground... you'll need the help. I'd suggest taking someone out with you for awhile too if at all possible... sometimes having a calm horse buddy will also help reassure a spooky horse until he can be weaned off on his own.
Other than that; just keep doing what you're doing! Go a little farther each time, and keep a strong confident attitude about you and the horse will pick that up and feel more assured that his leader doesn't think anything is scary.
Good luck, and be safe :)