Best route is not JHANG at the moment
I visit Islamabad 3/4 time / year and i would recommend following route
Multan-Chichawatni-Kamaliya-Tobateksingh-Gojra (Motorway-M4)-FSD(M3)-Islamabad
Kamaliya-Tobateksingh-Gojra is single road but in good condition and traffic is normal
Minimum travel time with two 15 min breaks is 7 hrs.