Adoption almost complete - 8 yr old acting up more

Our 8 year old son (whom we are in the process of adopting) has been acting up consistently for the past 2 -3 months.  It started with our first move.  We needed to get him into a better school and get closer to work so we moved.  He was very excited and looked forward to going to a new/better school, new town, closer to family, new friends, etc.  He has started lying more.  Even about little things like "Why did you come home early?  I thought you were playing with a friend?"  He told 5 different stories before admitting he came home because he saw me and my husband playing catch in the back yard.  He called me a liar today and when asked why by my husband he said he didn't do it.  On his last chance, before he would have gotten into even more trouble, he finally admitted it.  His listening and direction following skills are very poor.  He does extremely well in school though.  We've been doing work at home to keep him at, or above, his grade level since he was held back in kindergarten (by a previous foster home).  He uses "I don't know" or "I forgot" as an answer to almost any question you ask in regards to school work he gets wrong or when he misbehaves.  
I know that foster children have developmental and emotional issues most of the time.  We have come a LONG way since he first came to us almost 1 year ago.  He had a 2 hour and 4 hour tantrum the first weekend.  From Christmas until we moved in mid May his behavior was doing very well.  We are going to have him tested this year for any developmental delays and see if he has dyslexia, dyscalculia, or any processing disorders or developmental delays.  Many foster children have some, or all, of these problems.  Many of which go undetected or are labeled ADD, ADHD or ODD.  He did have PTSD due to abuse/neglect but thanks to therapy he no longer deals with that.  At 7 years old we had to teach him how to tie his shoes, bathe properly, read, do basic math, and basic spelling for his age.  He now reads at a 3rd/4th grade level and does 3rd grade math (multiplication, adding and carrying, subtracting and borrowing).  He is a very intelligent boy.  He just does not follow directions or pay attention very well (unless at school) and has problems telling the truth.  He says he's afraid to tell the truth cause it used to get him in trouble.  We told him that was then, this is now, and you've been with us long enough to know that.  We gave him tons of leway in the beginning and his punishments were losing "points" on a chart we had, or losing video games, or certain toys.  That no longer works.  We've taken tv priveleges, playing with neighbors, no video games, no toys, no tent, and given extra work.  Sometimes when he's upset about something he'll deliberately get the work problems wrong thinking we'll give up and just stop.
So, my question to you is this -  How do you get an 8 year old, that has had a very bad first 6 years of life (emotional/physical abuse/neglect/losing birth family/etc), to listen and follow directions and tell more truth than lies?

I don't want to spank him once he's adopted and I'm tired of taking things away since it doesn't do any good anymore.