I can get in 25 miles on a weekday and still arrive home by 6 p.m. He keeps a jacket, shoes, belt, deodorant and hair brush at the office. Shirt and pants go in a single pannier. As long as I don't overdress, I can get by with a quick sponge bath. Like other aspects of cycling, riding in traffic is a skill.
Confidence comes with experience.
Don't be intimidated. Even the best locks can be defeated with the right tools and enough time. Leaving your bike outdoors in the same spot day after day is asking for trouble. If possible, arrange indoor storage in an area inaccessible to the public. Organize your clothes and gear the night before.