boc My ds1 was also a FTT baby...his early weeks were like something out of a nightmare for us
He had undx IUGR (intrauterine growth restriction) so basically my placenta stopped working at about 32/34 weeks but it wasnt picked up. He was born at term weighing 4lbs 15 oz....he went down to 4.5lbs and was a very poorly baby indeed. He also had a strep infection in his blood which wasnt picked up til he was 6 weeks which didnt help matters! Also prolonged jaundice.
For a while they did query CP as he was so very floppy. He did not sit up unaided til he was nearly 10 months old.
I can really relate to your comment about a famine victim baby....I dont think my dear uncle (who passed away 18 months ago) ever got over his shock at seeing ds1 for the first time...he was 5.5lbs at this point and looked very poorly indeed
My aunt could fit his whole head in the palm of her hand 
Now however, he is a strapping 8 year old who is in the 75th centile for height and weight 
I think we are very lucky ds1 is as he is...in fact I know we are. He could so easily have much worse problems than he has.
AFAIK RRT is designed to pick up any retained primal reflexes - that we are all boen with like moro - and use the exercises to inhibit them and encourage the postural reflexes to take over - which should happen at 1-1.5 years old.
TH exercises are designed to stimulate the cerebellum (literal translation = small brain) at the base of the brain/top of spinal cord which in some kids with symptoms of dyslexia/adhd/dyspraxia etc are due to the cerebellum not functioning/not developng properly.
HTH x