Rad?

I am concerned my son may have some form of RADS. He is 7, came home at 11 months and was with the same foster family from birth until we 11 months of age. He can have tantrums when things do not go his way. These can last quite a long time 1-2 hours. They can be triggered by exposure to food coloring additives. Sometimes he will remove himself to his room on his own, but most of the time it is a fit that requires us to move him or even basket hold him. With my autistic students the basket hold calms them down, but instead this makes my son worse. These tantrums have not tapered as he aged like my BS who has aspergers. My son recently began saying swear words under his breath when frustrated at school. He does not get along at all with his older brother, but it is hard for 14 years olds with aspergers to relate to a 7 year old. We have felt he has attached to us. He hugs and kisses us, cries if he cannot find us in large crowds and says he loves us. I have had a few acquaintances mention they feel his behaviors seem like RAD. Love your insight on it. Thanks J