They have a 6 in 14 chance to be in that group, since the "group of 6" is in the east.
No. Atlanta won't be in the group of 6. They will be in one of the other two east groups.
There is one "seeded" team per group. Orlanda will be top seed of the 6 team group as the host team. Atlanta and Toroto will be the top seeds of the other 2 east groups.