You can't reinforce fear - it is totally alright to comfort a dog that's afraid. It helps build trust in you, which is way more important to helping a nervous dog than just letting him get over it. You may want to stop picking him up, however, and kneel down to comfort him, just so he doesn't continue into adulthood to expect you to pick him up when something scary happens.
Also, having a noise-sensitive dog myself, I would seek out the advice of an experienced, well-qualified trainer who is familiar with noise-sensitive dogs. It is possible that he is just going through a period of increased sensitivity - a fear period, and that his nervousness about those new things will decrease on its own. But noise fears - especially noises that are environmental and out of your control like traffic/cars - are really, really hard to work on by yourself.
Also, having a noise-sensitive dog myself, I would seek out the advice of an experienced, well-qualified trainer who is familiar with noise-sensitive dogs. It is possible that he is just going through a period of increased sensitivity - a fear period, and that his nervousness about those new things will decrease on its own. But noise fears - especially noises that are environmental and out of your control like traffic/cars - are really, really hard to work on by yourself.