I remember your previous threads. As I understand it, SS involvement was triggered by your exH's behaviour, but their involvement continued after the two of you split up, and they ultimately took you to court to remove the children from your care.
If that's right then it's quite clear that your current situation, for whatever reason, is not one that they believe to be right for the children. I don't think staying put and getting a degree is going to change that. If there is any hope of your children returning to your care then you are going to need to make, and sustain, substantial changes to your situation.
I would be thinking about moving near to your children - where you will presumably also have the support of your parents - and having as much day-to-day involvement in their lives as possible. Is there any reason why you can't take over some of the legwork involved in looking after children? Would your parents support this? You could do some schoolruns, cook some meals, help with homework etc etc.
The degree sounds like a long-term goal that may need to go on the back-burner while you get yourself set up in a new place. Find a job, find somewhere to live, re-establish regular contact, and then think about the degree.
Do you still have contact with SS? If so, it might be worth making those big changes and once you have a good set-up ask for a meeting with SS and your parents to discuss the way forward.
I know you say your DP had nothing to do with the children's removal, but the simple fact of you starting a new relationship at that time may have caused concerns. I have a lot of dealings with SS in my line of work, and I did a few months of family law when I was training, and I know that a new relationship - even one that ultimately turns out to be positive - is generally going to be an issue when there is SS involvement. The thinking is often that that the focus should be on the children, not on a new partner, and there can be concerns that someone is moving too quickly after a bad relationship.
You may find that if you are on your own, close to your children, working and re-building family relationships, SS become much more receptive to anything you have to say about the future. If you let the status quo remain for much longer, I'd be dubious about anything ever changing. Not just because of SS, but because your children are getting older, and children can get used to someone not being around. My father effectively absented himself for large chunks of my teenage years after my mother died, and I ultimately lost interest in seeing him. It was years before we got back in touch again. I have a family member who has had problems in relation to contact with his children and has let things slide. One of the two children now has now interest in having a relationship with him. A parent-child relationship needs work and input, like any other relationship, and you can't work on it fully from hundreds of miles away.
Good luck reaching a decision.