IIT

yes it's ryt decision 4 u. because ur marks simply reflects that u r hard working.
So if u have a strong will 2 do IIT. then go for it without any second thought. . .
N work hard.continuously 4 a year.
u will definitely get a good AIR. if u work hard 4 it.
BEST OF LUCK .

It depends up on the faculty, infrastructure and campus.

Admission in IIT is not based on 12th percentage it only depends on your Advanced rank. Since i don't know how was this year's paper but still at 150/372 its very hard to get good branch in any IIT. Also i'm not sure but the 12th percentage issue may also arise as one must have above 75% in boards.

IIT-Indian Institute of Technology
80% pcm students have craze about IIT.
There r many IITs in INDIA.approx 16.or i think this year will b more.
Top IITs.
-IIT BOMBAY
-IIT MADRAS
-IIT KHARAGPUR
-IIT KANPUR
-IIT ROORKEE
-IIT DELHI
-IIT ROPAR
-IIT GUWAHATI
and many more.

If u score well in jee mains n also ur %age in 12th boards is 70+ then ur chance of getting NIT will b higher.

Some of the main benefits-
-best faculties
-best facilities
-best resources
-best environment
-best placements
-best chances 4 great future.if u work hard.

It's three step process.
-first make ur % above 70 or 75 so that u can come into top 20 percentile.
-then clear jee main.clearing cutt off will b okk.
-then clear jee advanced with higher marks as possible as u can.so that u can get good rank.and desired IIT

Taking up Science stream will enable you to sit for JEE Main exam after class 12. When you qualify, that is, cross over the limit set in the JEE Mains, then you can sit for JEE Advance. Performing well in Advance will get you into a IIT.
Note: If you qualify well ahead of the limit in the Main but you didnt get enough marks in JEE Advanced, you can get into a NIT.

Yes, you can write the exam next year also. But do check the age limit. If you believe you can clear the JEE Advance and get into a IIT, only then repeat.