I know there is no exact amount and it differs per person but how many hours to get a 1300 on SAT 200 point increase…got a month so … 
-what would be the best thing to do to study for it?
There is no way you can know that. You can’t ask for time, but you need to practice.
If you only have a month then you definitely have to dedicate a couple of hours a day to practice new questions and try out around 2 practice tests per week.
All you can do is practice and not be lazy.
Depends on the individual. Only you know what you’re capable of.
i raised my score by 170 points in 1 month. im international student, learn grammar perfectly, do lots of practise tests (treat it like a real test, do full tests in OFFICIAL rules, so 65 mins for reading section for example and etc)
believe in yourself, ignore negative people around you, do your best.
best of luck