Residency Query

Hi There,

My company has been sponsoring (Tier 2) me since December 2012 and I have a visa until end of November 2018. I had entered the country in September 2009 as a student and would be a few months short of the 10 year period when my visa expires.
Unfortunately I have been dealing with a long term illness (was potentially life threatening) since end of December 2014 but am recovering and intend to start a phased return to work in a couple of months and hopefully go full time again by mid next year. I did manage to work part time for a few months (Sep 2015-Jan 2016). I am not sure when can I apply for my residency, but I do know from the discussions I have read that I will have to have a minimum salary of £35,000 before April 2018 and that of £35,800 beyond.
- Would I need to earn this sum for a specific period of my sponsorship, before I can apply for residency (like 3 months, 6 months or 1 year)?
- Would my time period under illness cause any issues towards my application of residency?
- My application of residency would depend on my salary as I understand. I am currently short by about £3000 of the £35,800. In case my company refuses to increase my salary, can I apply for residency/appeal under some exceptional circumstance where I couldn't work for almost 2 years and if I had, I could have potentially met the salary threshold?
- Also, if my company increases my salary, would I have to mention about my illness anywhere in my residency application? And would the CoS have to be updated with the new salary?