NOC 4012 documents required to prove work ex

I have a query if you may please help me.

I did my PhD from India and worked as a TA/RA during my PhD under UGC fellowship. I have managed to get a letter from my supervisor stating my work during my fellowship period. UGC used to send my salary to my university, which would disburse it directly to my bank account. I worked as a Junior Research Fellow from 2011 til 2014 and as a Senior Research Fellow from 2014 till 2016. My salary as a JRF was 16,000 per month and as an SRF was 25,000, with an HRA of 30%. However, there came a notice by UGC which raised the salary of SRF from 25,000 to 28,000. But the office order was released by my university in 2017 to pay the arrears of 3,000 per month retrospectively. I recently got the bank statements from my bank, which we unfortunately incomplete. But I do have a few entries sporadically where I can show the amount 16,000 and 25,000 credited. The arrears amount came in 2017, for which my bank did not give statement and I intend to request them again (which is a long process in India).

There are a few issues here:

  1. The salary written in my reference letter for SRF is 28,000. My university has apparently lost the office order which raised my amount of SRF from 25,000 to 28,000. I have the order number with me but they cannot trace it. If I got this I could have proven that I was getting 28,000.
  2. My university sometimes would disburse the money for odd periods. Forexample, they would disburse it for 1 month and 10 days. So in some bank entries the amount mentioned is 18,666.7 (an not 16,000). Similarly for SRF amounts. And some times they would merge this amount with House Rent Allowance and sometimes these two would be paid separately. And some times this would be compounded by paying salary for 3 months together, I tried bifurcating but doing it with all the entries is very complicated. How do I explain this in my explanation letter?
  3. If the chairperson of my department writes that I used to get SRF for 25,000 which got increased to 28,000 would that suffice?

Please help. Please suggest any other alternative documents which I can present to support my case. I would not be able to prove my work experience?