I went through that too.  It is sooooo hard to judge and there is no really clear answer.  I NEVER got an answer to your question about how quickly the meds are absorbed.  I’m not sure there is one.  I know I’m not offering much help, but I wanted you to know you are not alone.  I have two SWCAH children and giving the meds does get easier with age.  Trust your motherly instinct.