3. 0w40 should be perfectly fine. Technically it won't be as good as a more specific 0w30 in winter, but if you're not going to drive your car all that often in the winter and it's parked indoors, I don't think there's anything for you to worry about.
4. For the occasion drive these will be great. Given that you have the option to choose when to drive rather than having to daily it, I suspect you'll choose not to drive during snowstorms
. Like someone above mentioned, the only issue with these tires is when you drive them over deeply compacted snow.
5. If you suspect you have salt on your car, take it into a touchless, railless car wash. But as for preventative maintenance, if you have chips exposing bare metal like on the hood, you might want to consider using touch up paint to cover it up. I used Dr. Colorchip recently and it's super easy to do. Takes like 10 minutes to do for that added peace of mind.