You are honestly saying you worked knowingly below the award? and then renewed that but "wanted it in writing"
Sorry you are a problem, will you break minimums just to have a job too? or go 50kg over MTW every flight?
Taking the job in reduced circumstances shows that you were willing to go forward in good faith. I think that's admirable. I also think the employer was very lucky and should have repaid your good faith by upholding his end of the bargain.
The minimum is the minimum is the minimum. The good guys pay minimum or more. Honour yourself and honour the good guys by insisting on proper pay and conditions.