Hi lovely!
I can understand how frustrating this must be for you, I hope you're okay with everything going on. The same happened to my friend, her household income is less than £15k a year and they assessed her for the minimum amount without even contemplating any other amounts. She spoke to the finance officer at our college and was advised to call student finance up, once she did they told her that most of the time they will show the minimum amount but as the time gets closer to receiving payments and going to university, it increases and goes onto the actual amount. She told them she was anxious about this so they told her they would get someone to call her back. She is on holiday right now, so I'm unsure if it got sorted.
There are also some student finance reps on TSR! It sounds like they may have made a mistake as your circumstances do not add up to the minimum amount, I'd try calling up again and see what happens. I can totally understand your stress right now, I hope everything gets sorted!