I am a 50 yrs plus male living in Dubai.?

At the of 35 I by chance found out that I can sing and I can sing very well. I have an exact voice of Late Sh. Mukesh ji and my lehza and throw is same. Without any formal training sing in perfect sur and diction is also good. I have been singing professionally on stage with prominent singers , all over the world. My problem is that since i have been singing only Mukesh, my range is very limited. If I try to sing other new singers or songs, I am unable to sing on high notes , some mental block comes in. I was then advised to start clical training. I started but I cant cope up. I fumble on remembering notes , besides being a sr. management in a MNC , i do not have that kind of time. How can just do voice training to increase my range. Is any training possible by way of only Clical songs where I don't have learn and practice on ragas by sargam but by Aakaar and aalap. My objective is to go out side my Mukesh Range and be able to sing any film song or new composition with more perfection. At this age and time clical is heavy for me. Please give me the route I should follow. Please serious answers only .....