Add contacts to Marketing List

1. We have just started to use the Microsoft CRM solution in our company, and we are trying to make a Marketing List. We are able to add companies from a certain city to the list, but we would like to add contacts working for the various companies, and avoid bringing those who do not want to receive newsletters. 
   
   So say that we have Company A, B, C and D that is relevant for us. Each of those has 10 employers. We would like to add those 10 employers from each company, so that we end up with 40 people on our list. How do we do that?
   
   
2. Also, there seems to be an issue when searching for contacts. If we want a list out of people registered in our country, we only get about 240 people, where there should be thousands. What can be the problem? 
   
   
3. Last but not least, is it possible to change the sales responsible person for a set of customers in one operation? Say that one of our sales persons has 20 customers, and quits working for us. Then those 20 customers should be transferred to another sales responsible.

Thanks!