Hi,
I think I would try another GH kit. Your readings are really unusual.
If true.. I think your best bet is to use straight Ro and reconstitute with a commercial product. Normally I would suggest a tap water to Ro mix but your water as tested is really off.
Your KH is about 12 degrees hardness (214 ppm ÷17.9)
If you cut that in half with RO your kH will still be around 6 which will still buffer your water. If you want to lower your pH its probably best to use 100%RO.. You can try try using maybe10- 20% tap but with a GH of 0 I would be concerned traces are missing.
Al