anyone know if would be best to just remove the softner or just to keep it
You can remove the water softner completely. The softener removes the calcium and magnesium ions from the water and replaces them with sodium ions. Sodium ions are much kinder to r/o membranes.
The first thing I would do is remove the salt wash and replace both the prefilters, 1 with a sediment filter and the other a carbon block filter. Couple the inlet hose to the first prefilter (sediment) and direct the waste to a drain.
Open the waste tap totally and switch on the tap. Allow that to flush for a while, say 10 minutes. Then switch the water off. You then want to uncouple the pipe that goes from the r/o to the tank and put another length of hose on it. You need to do this so you can take pure water samples to test the tds of.
Switch tap water back on and slowly close the waste tap, but not completely. You need to get to a spot where the waste is about the same quantity as the pure. Take regular samples of the pure, slightly opening and closing the tap until you achieve the best result. As I said earlier, if the membrane is ok then you will be getting a tds of around 5-6.
If it isn't, then you will need to replace the membrane. Depending on water pressure, it will either be an HF4 or HF5.
If the membrane has been allowed to dry out or has stood idle for any length of time, then you may have to replace it - sorry.
Once you get the system sorted, then you can fill it with the correct salt and put it back in the system. You may need to phone Streamline and ask them when the salt needs to be changed and how you know when to change it.
I can't get you their telephone number. I have a lovely 82 page 2013 catalogue on my desk - not a telephone number or address to be seen anywhere - what a waste of money.