ACT Innovation outside of contract

This is my first post, and the first time I've publicly asked this question.

I was a government employee working in an ongoing role as a scientist. My job role description was written in 2016 and was broad. I developed innovations in this role as part of the job description but my employer constantly verbally claimed that these innovations were not central to the job role. Then my work was obtained by another employee who was a professor at a nearby university, and he published the findings of the work along with code that I gave him without crediting me as co-author.

At the time I engaged with my superiors and they did nothing except a verbal agreement to have me acknowledged in the last paragraph. I do not know if this was enacted. At this point I lost faith in my employer protecting my work and giving due credit.

Fast forward some months, I joined another team and began applying my knowledge and skills to develop new code and innovations. This work was presented at a distinguished lecture. I then had to quit my job for personal reasons and move back to my home city. After I quit, I engaged with a former team member and advisor and we agreed to develop further a concept that he had proposed a while back. Nobody else in the organisation could do it, I was unique. So, after my employment was terminated, I set about to develop the solution. I developed code that solves a novel problem and works very well. It built on my previous knowledge but it was applied in a new fashion and required lots of work to get right. We had email exchanges where he made suggestions to plotting code and descriptions. I registered a company with the intention of invoicing because this is my work. He then stated that they can't pay for this innovation, but he might try to get me other work with the organisation. This other work has not materialised.

Is the innovation I worked on my own work and as such can I prevent others in the organisation from taking my work (stealing it, in my eyes) and talking about it to stakeholders in negotiations to win contracts and eventually publish the work? I have not been credited, I have not been paid, and this organisation is notorious for convincing people to work hard and then claim "but it was fun, and we didn't sign a contract so we won't be crediting you or paying you but will claim it's ours without asking you." What are my rights to protect my work and be duly credited and paid, and how can ensure that this intellectual property remains with me?