Hey,
So answering the main question, the scholarship band is decided on your PCM(Physics, Chemistry and Maths) percentage.
We have 3 scholarship bands the details I am sharing below are for CBSE board:
Scholarship C(80-87%)
Scholarship B(87-94%)
Scholarship A(94%+)
Now depending on your PCM percentage you can find which scholarship you are eligible for.
Answering your subpart questions:
1.The University considers your JEE mains marks also for eligibility and scholarship bands, eligibility criteria for the same being 11o+ in JEE Mains(this answers question 2 also)
3. Being a student I can’t tell you what your chances are, all I can advice you is to give your SNUSAT+APT with a clear mind and to pay attention to the last 4 questions of the application form.
4. Scholarship bands and percentages are defined above which in-turn waive off the tuition fee. the living and administration expenses stay the same for every student