NIT

Some of universities like IPU and some others conduct lateral entry exams for second year while you can take admission this year and again appear for entrance exams.

Yes, chances are there. Last year thousands of seats were left vacant. Just wait and watch. I think the cutoff will fall up to 1-2 k for general category.

Your chances are very less but you can try CSAB counseling. You should wait till spot round. Although you can get integrated B.Sc+M.Sc courses in NIT- Patna, NIT-Rourkela and NIT-Agartala.

You can check the fee structure for different NITs by visiting their official sites.

You can take admission in NITs or any government college only if your PCM percentage is above 45%. But you are in reserved category so you can get admission anywhere.

The counselling for NITs, IIITs, GFTIs and IITs will be held after the results of JEE Advanced. You need to look for counselling at www.josaa.nic.in.

No, you will not get any of the NITs with 43 marks. Cutoffs for NITs are too high to admission on the basis of JEE Mains.

Yes, there are some chances for you to get some NITs like Goa, Hamirpur, etc. according to previous year official closing and opening ranks.
As you have qualified JEE Mains and your category rank is also decent, you can get some NITs.
You may refer the link below to know your chances of getting a college:
http://josaa.nic.in/Result2016/result/OpeningClosingRank.aspx
This link gives the previous year ranks for each NIT , IIIT, etc. These ranks vary each year so that this may give you an idea.

Yes, your chances are good. You may get admission in NIT, Warangal for CSE.