So after the boil, you topped off with 0.8g. Next time, use 0.8g more sparge water, and you won't have to top off at all. Using the extra sparge water will also rinse out more fermentables, giving you a lower gravity for your final runnings. A final runnings gravity of 1.038 is very high. When you add your sparge water, do you stir it really well? With a batch sparge, it is the stirring that dissolves the sugars, and if you don't stir enough, you will get low efficiency.