OP, I am sorry sorry that he has done this to you and to your children.
His comments are classic coercive control. It sounds as though he has isolated you from friends and family and now he is undermining you, gaslighting you and telling you that only he cares about you and will support you.
This is not true.
You are worth love and respect in your own right and there will be someone to care about you and take care of you in your future.
For now, I would recommend contacting Women's Aid to get some concrete support. He has committed financial abuse, and by not giving you the £2,000 that he does have, he is controlling you.
To other posters, on the face of it, the OP may appear to have been foolish, but men like this are clever about what they do. He may have encouraged her to use his account. The higher interest only makes sense if he kept it in the account. So while the OP could have invested the money better, we have no idea if she was coerced by him to take the action she did.
Women who are controlled often feel things are their fault, when they have been manipulated into the situation. So please show some kindness and support.