B.Arch

Some suggestions be:
1- A Complete Self Study Guide for B.Arch. Entrance Examination by P K Mishra
2- Steps to Architecture NATA B.Arch. Entrance Exam Paper Guide Paperback by Nimish Madan
3- Steps to Architecture: B.Arch. (NATA/JEE Main) Exam Guide Paperback by Nimish Madan
4- NATA and B.Arch. Complete Self Study Material by Ar. Shadan Usmani

Yes, you can get into B.Arch with these marks into DY Patil School of Architecture.
Since, the cutoffs are dynamic and this data is based on 2016, so it may change and things may not turn in your favour. Although, your admission is more in your favour.

You are likely to get the best colleges in India with such a big rank. I would suggest NIT Trichy, NIT Kozhikode, BMS College of Engineering, College of Architecture, Chandigarh and RV College of Engineering.
Note: Kindly check the least board marks for colleges as mostly for general, these marks are 75% in 12th.

Yes, there are many colleges which accept Mains paper - 2 as well, still there are many which accept only NATA. Some recommendations are BMS College or Engineering, NIT Trichy, NIT Kozhikode and RV College of Architecture.

You can get a seat in NIT-Kozhikode, NIT-Trichy (less likely), RV College of Engineering, Modi University and BMS College of Engineering.

I think you should probably go for private universities like Amity University, Modi University, Manipal University and LPU. These universities have good placements.

Yes, according to your marks combined with your category, you'll definitely get into VNIT. Moreover, I would suggest you to go for better NITs as there are higher possibilities for them too.

You'll only get private colleges with this rank.

Enter your score and check here:
https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor&ved=2ahUKEwjUpLbay7bbAhUR448KHeU8DUkQFjAAegQICRAB&usg=AOvVaw1N9BzFtyUCP4JU-2UQHQ0H.

Admissions to B.Arch is based on NATA/JEE only.