Teacher

Well, for this year, the central government has no such plans to add any new colleges for B.Ed.
There are no plans by the central government to offer B.Ed for free.

Yes, IGNOU provides that opportunity.

No, you can also work in teaching field after BDS but the salary after it will be less.

One thing is that you can't get a permanent lectureship with only B.Tech in your hand. As per the new AICTE regulations, there are no lecture posts in engineering colleges anymore. The name of the first lectureship post is Assistant Professor. So you do need a PG (in your case M.Tech.) to enter into the lectureship. You do get lectureship as a guest in some self-financing engineering colleges or in poly techniques.
If you take your PhD, then you can start your career as an Associate Professor (Professor if there is vacancy).

You need to pursue B.Ed after completing UG.

No, you cannot. BA and B.Ed are compulsory for TGT.

All the teachers are partly dependable. I speak from my personal experience. If the scripts are given to a different teacher, you may be disappointed. I suggest that you should do your best and then depend on your teacher.

You have a pretty good experience in IT. Why do you wish to switch?
To become a high school level teacher, you should at least graduate with a B.Ed degree and you should have cleared CTET or STET to be able to teach till 8th grade. 9 and above grades don't require you to clear these papers but B.Ed and graduation only. To become a secondary level teacher, you should be a post graduate with B.Ed

B.Ed is very necessary for one who do not have exposure to different levels of teaching.

You shall complete your PG along with B.Ed. I hope this would suffice.