Exam

I think not possible with 54000 rank to get admission.

Yes, but it depends on the branch you choose.

JSS is quite difficult, but you can easily get AKG or KIET.

6 or 6.5 band is sufficient, but you will also need proof of German language proficiency.

NIT Jamshedpur is a good option with EEE. It has good package around INR 10 lakh per annum and is doing well. Moreover, you have better options with CSE in MANIT Bhopal or in MVNIT, Jaipur.
You can compare colleges using the rank predictor:
https://www.shiksha.com/b-tech/resources/jee-mains-college-p

Yes. You should ignore the exam of the optional subject in PUBDET.

You have some chance for getting government colleges. Go for counselling.

Even I also scored 70% in PCM and dropped 1 year for preparing NDA as well as class 12th improvement. Wasting a year for preparing NDA is a bad idea. I myself have done this that's why it is quite a personal like question for me. Go on your with your studies. As at SSB, I found many aspirant were ei

Please use Shiksha college Predictor by your rank card.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor.