RAD characteristics when removed at a young age?

Our soon to be adopted son is now 2 1/2 years old and we have had him since 3 months old. He was with his grandma the first few months until she was deemed to not be able to keep him safe from mom. Mom has multiple mental disorders...bipolar, schizophrenic, etc. She gets violent when not on her meds. I don't believe our son was ever directly abused (although not positive) but she would often be holding him while having her meltdowns (throwing chairs, ripping out screens, banging her head against the wall, etc.) He was so traumatized as an infant...refused to be held facing in (had to keep an eye on surroundings), rocked constantly, meltdowns that lasted hours, had severe hypertonia from stress, etc. Thankfully, he has come a long, long way and he is a very high spirited toddler, but most of the time functions fairly normally. He still gets monthly visits with mom, never had any contact with a father figure. Visits will drop to twice yearly at adoption, which hopefully will be soon. Anyway, I've noticed in the past few months that a lot of his more "dysfunctional" traits that still exist parallel a lot of stories that I have heard on here in the past with kids with some degree of RAD or a similar condition. Namely, he is VERY manipulative and knows exactly how to get what he wants from whom he wants. I know toddlers can do that normally, but he is extreme and very purposeful...for example, he knows he has specific boundaries at home but when I take him to work with me (I work in childwatch at the Y) he turns into a different child knowing he can't get put in time out or anything...he will stare at me across the room with a stoic look and toss toy after toy across the room waiting for me to react. If another teacher steps in, he flips out on them and gets violent. If I step in, his behavior escalates. If I don't step in, it escalates. He also can disconnect very easily emotionally, when he is getting talked to about something or we are asking him to focus, his face just goes...blank and he checks out. It's really eerie. He is able to switch from freaking out meltdown to over the top cheeriness instantly and then back again. He still can get violent to himself or others when angry. Anyway...I guess my question is, does anyone have experience with a child removed at such a young age still having issues with RAD type characteristics and what were some things you did to help your child work through that?