The contract is not enforceable. Lawyers in India does seem to love them but in fact they are not enforceable as indentured labour is illegal in India. Any employee may leave a job any time with or without resignation, and cannot be compelled to work without their wishes. Notice period is a courtesy and not the right of any organisation. As such You will have to pay him the salary, minus any amount you spent on training him.
You can legally withhold his experience certificate or give him a bad review in the experience certificate. That is your right. But you can’t hold on to his salary. At this moment what you can do is terminate him on the basis of repeated non communication and repeated instances of not showing up for work without prior notice or intimation after the fact. But you will have to pay him the full and final settlement till his last working day.