I wouldn't raise it beyond where you are now without first reading up on the effects of high mag from a reliable source. There is no benefit in doing this unless you are trying to rid your tank of Bryopsis. And it didn't look as though you had any growing. It takes a tremendous amount of mag supplement to raise it, and in doing so, also raises the salinity.
I had to raise the mag in my tank from 1000 to 1300 about 6 months ago because of the salt I had been using, this raised my salinity from 1.026 to 1.029. I think it is from the chloride. Someone correct me if I'm wrong here.