Engineering Entrance Exam

Taking one extra year generally does no good. If you have any chance in KIIT, then go for it. Never try to look back. If you wait one extra year to pursue JEE, you will be bored and most probably start hating studies. Just go ahead but be amongst the best.
All the best.

If you belong to any of the reserved category, you are very soon getting into an NIT. But if you belong to general category, you may or may not get any of the NITs.

Which entrance exam rank are you talking about?

Pass mark (Cutoff ) for OBC in JEE Mains is 70.

100 marks would be sufficient. exact marks will depend on cutoff.

No, you won't be able to get into the college because of your low marks in JEE Mains exam. Even though you have scored really well in the HP Board exams, you would need to get more marks in JEE to get into this college. Also, please specify the branch you want to get into so that I can tell you the cut-offs of that branch. You will need to score around 150 in JEE Mains to get a good branch at NIT Hamirpur.

yes u can but now prepare for advance

With your credentials you can get Information technology at BIT Mesra and School of Engineering & Technology, Mizoram. Other top tier colleges will be hard to get.