I agree with LIA, depending on the local laws, my first port of call would be a lawyer's office.
A workplace should be somewhere where you feel valued, where you are respected and most of all feel safe! None of those apply in your situation.
I hate to say this but you must resign now, I realise you have responsiblities outside the workplace that make this hard, but the long-term effect this workplace is having on you is worse than being unemployed.
If it's difficult for you to find another IT role, how about another job, temporarily, until another IT job comes along?
Honestly you need to leave now, sorry.
With regard to covering letters, try and tailor make them for the prospective employer, and as LIA said highlight all the responsibilities you have taken on at your current job.