Good to see someone from Uttarakhand interested in Thapar University but let me make some of your facts clear.

PS: There is no Uttarakhand quota in Thapar

1)Thapar University doesn't have any quota for defence persons however you may get a scholarship under the scheme from government of India.

2)As the university doesn't conduct conduct counselling on the basis of Jee Mains rank rather it is done on your Jee Mains score,so the odds are not in your favour .

3)70 is too less to qualify for core branches,you might be able to get chemical eng.

4)In Thapar University there is no such stream as IT rather we have

(i) B.E.  Machine Learning and Data Analytics

(ii)B.E. Software Eng

(iii)B.E. Computer Animation and Gaming.

If you are interested in IT you may check the website mentioned below but lets face the truth you have very minute chances .

Dhirubhai Ambani Institute of Information and Communication Technology

There is no good private college that will allow you admission on  such a score in Jee Mains.You will surely get  Jaypee University(but that's not a good college) and Nirma University Ahemdabad ( Nirma University )

You can try your luck at Govind Ballabh Pant Engineering College, Pauri Garhwal ,here you have 99% chances of getting a good branch under state quota.