In the section for Actual expenses for my vehicle for the year, should I total expenses of all businesses using the one vehicle or for one specific business?

Yes, enter vehicle expenses for each business as if there was a different vehicle for each business. 

If you have only one vehicle that is used for more than one business, enter the same vehicle information, and beginning/ending mileage (or total/commuting miles) for each business.

However, the actual business miles for each business would be different.