What is torque of Benelli TNT 600?

Depends up on your need , but it is one of the good sounding bike of this range. cost around 4- 8 k depends upon the way you use bike. but mind-it, it is not utility bike hence service may not be cheap.

First you tell me what is your purpose if you need sound and you like a L line 4 cylinder engine then my suggest is you go for benelli 600i otherwise as a bike performa Ninja 650 is better than benelli 600i

Chain kit is not needed to change often, as it is durable part of bike. unless you use it rough or got bruised due to rust or fall.- ixil is an awesome exhaust, i have anniversary edition of it, few things can be noticed once you install exhaust- BHP will increase a bit- sounds awesome, ear orgasm- you will make bike light weight a bit that will increase efficiency, hence mileage may increase a big, but on thing if you dream of big bike mileage is not the first factor.

No, the bike is low on any of the modern features and the price point except 4 cylinder engine and sound and build quality nothing is special.

My height is 5.3, i can hardly reach the ground. I don't own a 600i but did a test ride. Its a bit hard to control the bike but i guess i can managed after a while. But won't be as manageable as an average of 5.7 or above person. I guess a 5.5 person will be able to manage the bike too, but it may take a while to get used to. Just do a test ride and see for yourselve.

It’ll cost you anywhere between 4-6k for your first service

Yes yes of course I think so