Hello. TDS can be deceiving because it depends on what the mineral content is. When I add salt to a tank when treating for an illness, my TDS can soar over 3000. Even in a breeder tank, this high TDS will not affect breeding because the high number is sodium. If you can get a test kit and measure GH and KH it will give you a better idea of how hard the water truly is.
If your high TDS is because of high mineral content, the best way to reduce the hardness is by using an RO unit and mix 50/50 RO and tap water. I don't know if your hard water would be bad for your discus because I've never heard of water that hard, but my water is in the 400 range total hardness and they thrive.
As far as ph goes, don't be concerned with high or low ph, be concerned with consistent ph...
Brian