First of all, I do not feel that it would be right to leave any dog home alone for seven hours at a time (i.e from 8:00 am - 3:00 pm). Dogs are pack animals. They are social animals. Dogs get anxious and upset if left home alone for long periods of time. They can also get separation anxiety. They can also become bored and destructive when left alone for long periods of time, such as from 8:00 am - 3:00 pm.
However, if there is someone else at home who is good with dogs and knows a lot about and is kind to them and responsible, the dog should be okay. It is advisable to ensure that the person is also capable of exercising the dog properly. If this is the case, please ask them politely to walk the dog and play with them (appropriate games only, don't play fetch with sticks and stones as you could hurt the dog and, due to concerns over it causing dominance issues, you may also want to stay clear of tug-of-war with your dog). If there are no other people would be able and willing to do this, and suitable for the job, please hire a professional dog-sitter, or consult the services of a good dog-walker. Alternatively, if you have any knowledgeable, dog-loving friends and/or family members who are kind, you could also ask them politely if they could dog-sit for you.
Before you add any dog of any breed or type to your household, please make sure for 100% that you and your lifestyle, home and situation are suitable. You also need to make sure that any other people who live with you are okay with your having a dog. You also need to make sure that your new dog will live happily with any other companion animals that you may have. If you have animals like chickens, geese, turkeys, cattle, sheep, horses, goats, etc, you will also need to take them into account (geese and other birds may peck the dog, and the dog may chase them and/or other animals). Please complete this quiz/test and see your result. Please do not get a dog if the quiz/test does not think that it would be a good idea for you at the moment. http://dogtime.com/quiz/am-i-ready-for-a...
As for the breed, I used a dog breed selector app called Perfect Dog. One of the excellent matches that came up based on some of your criteria that you mentioned in the question was the Lowchen. Lowchens are generally around 13 inches tall and come from Europe. The name "Lowchen" means "little lion" in German. These little dogs are seen in art pieces that date back as far as the 16th century. Lowchens like exercise but are not too demanding in that regard. They are known to generally be obedient, and can live well in smaller homes (but are, generally, not ideal for city apartments). They are fairly good with children, can be perhaps surprisingly assertive for a small dog and can live in climates that are mid-way between very cold and very warm (e.g. England and certain parts of the USA). Lowchens are also generally known to be somewhat sociable. With a Lowchen as a companion dog, you also have the benefit of having a dog that was actually bred originally to be a companion, as opposed to a Siberian husky, for instance, which were bred for work pulling sleds and as such are known to be very demanding when it comes to exercise and not suitable as a companion dog for people who want a sedate, relaxed companion that is happy to live in an urban home and setting and just go for a sedate 20-minute walk every day.
Finally, please consider adopting a rescue dog. Rescue dogs are not always badly-behaved, aggressive or too damaged mentally to be successfully rehomed. http://www.humanesociety.org/issues/adop...
Warning: This page contains information about dogs that are in danger of being killed by lethal injection or gas if not adopted within certain amounts of time (by certain dates). It also contains photos of said dogs, and dogs that have already been killed. It also may contain other images and/or information relating to animal cruelty. http://www.dogsindanger.com/
Best of luck.