I'm sure you heard this before was the tank cycled
what did you use for ammonia source
looking at your readings it don't look like you cycled
Cycle your salt tank - Aquarium Advice
a piece of a deli shrimp would be a good ammonia source to start a cycle
as for your ph levels I wouldn't be to concerned about that at the moment concentrate on cycling .
ph will fluctuate during winter months ph levels will decrease as air gas exchange is lower due to no open windows during colder months
once summer comes you will see improvement on ph once windows start being opened increasing air gas exchange
ph will also be higher during the day and lower at night
so long as you stay in the range of 7,8 and 8.4 your ok on ph