I buy the oil myself from a trusted shop or petrol pump. To get it changed any oil change place would do fine , i usually went to nadeem filter house which is near chuburji , its a bit far away from dha but they had the right oil filter aswell.
Don't take it for any checkup besides oil/oilfilter change. The air filter can just ble blown with an air compressor.
Do not use synthetic oil in it as it isn't designed to burn and will leave alot of carbon deposits inside the engine which can then make the apex seals lock up and your engine will need a rebuild.
You do know that you have to let the car warm up for at least 10 min when its cold and then you can start driving it when the temp gauge is close to the middle. And you should redline it once a day atleast because that will prevent carbon from building up inside your engine.
After you have had a nice drive let the car rest for 5 min especially in this hot weather.
Yeah Osaka coolant is fine , keep a good eye on the coolant level aswell.
Dont forget to check the engine oil regularly as the OMP (Oil Monitoring Pump) pumps the same engine oil you put in your engine , it does that to lube up the apex seals and side seals. So check the oil regularly and top it up if its near MIN mark on the dipstick