Help with benefits?

Hello there :) 

I have been trying to navigate the UK benefits system but it seems impossible to speak to just *one person* to get an understanding about what are the options. There are pages and pages of information, including on this website, but I don't know which of the categories applies to me. I find it really overwhelming.

Maybe if someone has experience of this system they can help guide me? 

I have looked at universal credit, but from what I understand they won't let me have this because I have £XXXX sum of money in savings. They deny requests from anyone with savings over a certain amount. So UC is off the table.

Tax credits - I can't get my head around how these work or even really what they are? 

PIP - I understand that this is only for people who need physical or practical help living day-to-day. I don't think I meet these criteria, as I live alone and do everything myself (washing, cooking, etc).

Council tax benefits - I don't understand/know how to claim. 

Help with rent - I don't understand/know how to claim. 

A little bit about me: I work part-time, about 27hrs a week and earn about 21k a year. I live alone. No children. As well as Autism, I also have complex PTSD, ADHD, Dyspraxia, etc. 

The issue I'm encountering is that because of my mental health/autism, I'm not able to work full time and so need help topping up my income which I understand the government will do, but I am not sure....how? I did work full time until about a year ago when the burnout just got too much and I had to ask my work to reduce my hours.

Thank you so much to anyone reading and/or replying! I wasn't sure where to turn but someone on a Facebook autism page said you might be able to help :)