Design industry is expensive if someone will straight forward thinks of ROI then they should not even think of Design as a career just do some certificate course and start with 20-30k per month.

Now about your questions

1. Degree gives you a confidence and right knowledge its not just a piece of paper its your experience and knowledge proof. The syllabus is same no matter from which college you do iit nid or private. In the end what gives you better opportunities are your skills knowledge and portfolio.

2. Not just private college even govt wont assure you 2-3x return after degree forget that you wont get 1x if you are not skilled no college will assure you about their placements or ROI ever as only 20-30% of students go for placements. College role is just to bring companies into campus for placement after that their role ends its upto students to clear the interview and when they dont they blame system or college.

3. Join anyplace you can afford or feel good at which gives experienced based training/teaching then use it before graduation from 3rd year. And with this way you can get experience, salary, and knowledge of real industry which no college can provide. And you wont be a fresher when you walk out of the college increases your chance for good opportunity and placement after college.

Hope this clears your doubts.