Be very leary about upsizing your pump. The additional flow may work against itself overcoming the friction of the 1/5" pipe. Most often the pump was intentionally set as 1 hp because your hydraullic system was designed with a 1 hp pump. to move up in size might require larger eyeballs in the returns at the pool and or swapping out the 1.5" for 2" pipe.

If youre losing sand from the sand filter, perhaps its a crushed lateral down in the the bottom of the sand tank. When was the last time your sand was changed? If its been several years like 5+, nows a good time and you'll have the opportunity to inspect/replace a broken lateral.