Best I can tell, the current pump is producing around 52 GPM @ 54' of head and a new 3/4 HP Superpump would produce around 32 GPM @ 21' of head (note head loss is not a constant and depends upon flow rate). The lower flow rate is because the current pump is a full rated pump and the Superpump is an up rated pump.

Also, sand filter are much more robust than most filters so although your current pump is exceeding the recommendations, it is probably not enough to really damage the filter. However, the filter is very small and you might want to up size that at some point.