Hello sahil,
I understand what you say and what your requirement is. Firstly , i am sorry i can’t send the screenshot where i could show you how and where to change symbol rate at the moment. Shall attach it once i reach the university lab. Please check the simulation layout parameters , there is where you find it. Hopefully i will upload it in some time.
Secondly i want to tell you that you can increase power to any value as per your requirement but within ITU-T standards. Increase power to 5dbm. It will work fine..hope it helps you.
Regards