I believe 144 corresponds to the 99.8 percentile. So your son scored in the top two tenths of a percent for verbal abilities. Definitions of gifted differ but usually a score of 130 or above on the WISC-IV is considered gifted.

I couldn't hazard a guess about the PRI score. My daughter also scored significantly lower on PRI than on VCI. In her case, she has trouble with visual/motor integration.