@lisaew,
Villa Clelia looks like a very comfortable B&B, and it's great that they provide transport to and from the station on arrival and departure.
You shouldn't have any concerns walking from the B&B to the station during daylight hours, as there will be lots of people on the streets, including the last stretch from about Corso Roma to the station. Use Google Street View to have a look at the route, so that you have some idea what it looks like. You may also be fine returning to Levanto at 22:00 as there will likely be other passengers walking the same route. I'd have no hesitation at all in walking from the station at night. However if you're concerned about safety, a Taxi is certainly an option. I'd suggest asking the hosts at your B&B for suggestions on that.
I've never heard that Taxi fare in Levanto begins at €10, so will have to leave that question for one of the others. I always budget for a few Taxi rides during trips, as sometimes that's the best and easiest option.