Advertising display on car

Putting display material that advertises your business on your car doesn’t change the use of your car from personal use to business use. If you use this car for commuting or other personal uses, you still can’t deduct your expenses for those uses.

https://www.irs.gov/publications/p463#en_US_2024_publink100033921

For the second scenario, is the spouse an employee, contractor or co-owner?  If not, then no.  If yes ... there MIGHT be occasions when it is deductible, but those would likely be infrequent.