coralbandit breeds gbr - he suggest around 100 tds but he or someone else noted they will breed in harder water. I think from the very limited experience I have they are just very finicky about change (tds, temp, ...) and prefer a very very stable and clean environment but I didn't have huge long term success with gbr so you might want to ignore myself.
I will say that my tap water is like 120 and the tanks are like 140.
Why salt ? That won't work with rams at all IMO ..
I am not a fan of salt at all..My only advice about is don't use it ..
After I have no experience to speak of with besides in a marine aquarium .
197 might work for the rams eggs ..
Checking your tap water is great but I suggest you get a baseline. Check after a filter and water change, when your tank is the "cleanest" that would be your baseline without adding salt of course. Then keep it somewhere in that range. I just cleaned my canister and did a water change on my 16 gallon and my tds is 163, it was 210 before. Fun little tool if you use it correctly