Bacterial chromosomes are actually more predominatly circular, I cannot think of a species with a linear chromosome. Plasmids may also by linear.
Bacteria do not posses chromatids, during replication a septum is formed to seperate the replicated chromosome, I believe centromeres do play a role in helping to bring each chromosome to opposite sides of the replicating cell before the septum forms.
Bacterial chromosomes and plasmids may both be covered in protein as there will be activators, repressors, polymerases, etc... bound to each in varying amounts depending on external and internal cellular conditions.
Size: for example E. coli has ~4.2 million baspairs while plasmids typically range from as small as several hundred to ~40 thousand bas pairs.
#6 it is true that bacterial chromosomes are not typically used as gene carriers however if a bacterial cell were to be destroyed and at least sections of the bacterial chromosome remained intact, other cells would be able to reuptake that genetic information which would confer new genes to that cell provided it was not of the same species.
#7 Plasmids typically carry antibiotic resistant genes and are used in conjugation to "share" genes between other cells of its species. However, genes used in antigenic variation, antimicrobial peptides, and other "specialty" functions will also be found on plasmids.