The best way to deal with your driving anxiety is choosing the passage over the mountains rather than the tunnel road. People race through tunnels, a passage is far more relaxed and quaint.
Never mind pass roads still are considered highways here in Switzerland. Thus there’s both a lower and upper speed limit, the latter the same as many tunnels’, i.e. 80 km/h. Hey, you’re 68 years old, live in the hilly Canton of Nidwalden, and you have half a century of driving panic under your rather taut belt. Neither serpentine corners – secured by flimsy posts marking the divide between the road and a 300 meters drop – nor irate bus drivers tied to a schedule which doesn’t allow for forty kilometers at 20 mph, nor possibly intoxicated tourists riding their BMW race bikes will make things worse. Will they?
Call it confrontation therapy if you may.
For maximum therapeutic effect, never use one of the abundant sightseeing platforms to swerve off the main road, letting them two dozen irritated drivers behind you pass. It’s passage, not pass, after all.
Also, constant driving speed is overrated, especially on roads where cows might stumble onto your path. The cue of drivers behind you won’t mind to adjust their driving speed by plus/minus 20 km/h to your insecurity and every whim. No, never. What a novel idea.