Currently, if they technically own the code, your open-sourcing it isn’t valid. You can put an Apache license in the repo, but you can’t legally give a license to others to use something you don’t actually own.

So the code is not really open source until someone puts that license on it with company authority. It is just public.

It sounds like this product competes with their other products. Even if they didn’t ask you to turn over control you would have problems working for them during the day, competing with them in the evening. Possibly liability even.

If you want control, and want to use it to do things they don’t want, you probably have to leave the company.

If you are going to leave, it seems you might turn over the repo to them to avoid legal trouble, and then be sure that someone else at the coming makes the open-source status official. Then you or others can fork it. But it seems you should only do further work on the fork if and after leaving.

Again this should not be construed as real legal advice as I am not a lawyer.