Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Half way to ocean water is 1 tablespoon per liter of water. You are about 1/4 or more of the way there, though a 'Rounded' anything is difficult to assess.
A hydrometer made for marine aquariums won't measure low levels of salt. I doubt it will show your current level very well. It might, though, and it is worth taking it out of the package and trying.
When adding salt for a fish GO SLOW.
1 tablespoon per 5 gallons is a lot to add all at one time. If the fish is OK at this level, give it a day or two to get used to that amount before you add more.
Mix the amount of salt with some water, and add it slowly over several hours. I would not add more than 1 tablespoon per 5 gallons, not even a rounded tablespoon, every couple of days.
It might be that the amount you have in there now is all you need to add.