350 litres is around 90g (US) so you should be aiming for around 1lbs (0.45kgs) of live rock per gallon which you're just under at 88lbs (40kgs). IMO you can never have enough live rock so I would increase the amount in the tank as much as you can. I had a 450 litre tank (120g) with around 85kgs (188lbs) of live rock and it still looked a little empty to me.
Do you have 'a' powerhead or more than one? If you only have one get more as you should be aiming for at least 20x turnover for a reef tank which in your case is around 7000lph (1850gph).
As for chemicals..........why? If the tank is new then the salt mix will have put in all the essential elements you need. You should not need to be adding anything unless you are having to buffer the pH or modify it in any way. You should certainly not be adding anything that you can not test for with some degree of accuracy as this can lead to major trouble. Partial water changes are the best way to add chemical elements to the tank safely.