Good back links are back links coming from strong trusted web sites that are related to your web site, while bad back links are back links coming from web sites that are not related to your web site content, spammy web sites.
No, it's not necessary for the keywords to be presented within the title, but they should be presented within your web site content. However, it is better if they are presented in the title as well as the content.
Page rank and web site ranking are related. A web sites ranking in search engine depends on many factors that play important roles in page rank, such as the number of sites/pages/votes linking/voting to a web sites, content, etc.
Can you elaborate more on your web hosting requirements such as; web space, bandwidth, location and any other information that would help us point you in the right direction.
It depends on why your account has been limited, contact their support department to assist you remove the limitation. Usually they will ask for some documents which you will need to provide.