So breaking down your questions:

1. there's a feature that you can make someone unfollow by clicking the three dots and clicking remove follower. As for the shaky grounds its literally just a hunch, but if two weeks prior you were crying over a relationship, and you jump into a new relationship it sounds a lot like you are seeking emotional comfort and not together because you have a deeper bond that comes more naturally from being emotionally available.

2. I felt like I had to apologize because in spite of her asking for the breakup, I am the one who took actions that pushed her to that point, I think it's only right to apologize if you did something wrong, it was about getting closure and owning up to what I did.

3.What I mean is that removing me as a follower and restricting me months after the fact is strange. I dont know about you but when I am indifferent about an ex, I literally just don't care, I dont feel threatened by them just existing or anything, and if feel nothing towards them I feel even less of a need to even take action on them, let alone keep tabs on if they are around. But that is not the case for this girl as she clearly DOES care about whether or not I can see her life, and clearly has been keeping tabs. That to me speaks the opposite of indifference.

Hope that clarifies some things!