Nile air and air cairo
4500 is so good
Another airports are much cheaper specially to SAW sabiha airport
Another cities ,mostly needs flights and about transportation ,buses and metro bus is nt expensive as taxi,and you can check buses timing and stations from google map so its easy and accurate
30 or 40 LT is so fine for your daily needs
Istanbul can be fully visited in a week
Download TripAdvisor,Traffi,metro Istanbul applications ,those will help u alot