Do I need to declare a private mortgage agreement as part of income/savings?

When it comes to finances and stuff like this I'm completely brainless so benefit of the doubt lol

My dad unexpectedly passed away in 2021 and did not write a will, and the house he owned and my brother and I grew up in was left to us with shared ownership. During a time in 2022 when I was severely mentally unwell and going through financial abuse, my brother set up a private mortgage agreement in which he pays me £800 installments each month for I think its 9 years until he has paid off my share of the house (98k). I receive 800 a month which goes towards my bills, i have no access to any lump sum, he pays me out of his pocket. I think theres around 66k left, but I do not know. I don't really know how it works or what I was signing bc i wasnt well lol, I just remember signing stuff with soliciters and now I receive this money.

I am currently a student nurse and I am in financial hardship as I am not fit for work and so cannot work part time, my student loan is not enough to cover living expenses and so I am awaiting for my PIP assessment and ESA assessment. When looking at benefit calculators (e.g, I am currently looking to apply for help with NHS costs as I require monthly prescriptions), it asks me if I have 16k+ in savings, capital, property etc. As I say I am completely brainless when it comes to stuff like this - note I have autism and ADHD.

Does this count as this? Does the 800 count as income (it is tax free)?, Do I say i have 66k in savings as thats whats left of the house even though I have no access to this money and it literally doesnt exist?

My brother lives in the house still, I have not lived there since 2021 and do not plan on ever living there again.