My dad lies. Please help

Okay so this is a bit difficult to explain because there's so much and the whole ordeal stretches to before I was even born (I'm 18 now). I'm also not the smartest individual so apologies if I'm difficult to understand. My dad is known for lying a lot, he's been to prison for stealing money but I know he's a good guy. We've had money troubles my whole life which has resulted in my mum's rage, often lashing out at my dad mostly verbally but on rare occasions physically. Recently it came to light that the man looking over the evidence of his case had also framed him (at the time no one believed him), and apparently due to paperwork problems his sentence lasted longer than it should have. He appealed this during and after his release meaning he's owed compensation for time lost and for the misjudgment of his sentence (he served 3 years and according to my dad should only have served around 6 months). He was released in 2010. It's now 2016 and we've received no money from his apparent appeal. According to him interest has been building up and all the money combined could be worth over a million British pounds. His account was also frozen meaning we lost a bunch of our own money and we still can't access it. Obviously he has a history of lying, twice we've been evicted from our homes with 12 hours to leave because he was too scared to tell us that we had an eviction notice months before (I think he tried to handle the situation himself). The first time we were evicted was merely weeks after the death of my brother who sadly committed suicide in 2013. That year we spent Christmas in hotels. Over the years my mum lost her confidence and sanity, she no longer works and is too afraid to even make a phone call to anyone but her family and close friends. Dad handles those for her which causes even more confusion and conflict. My parents have been promising me all sorts. They say I will get my own flat, we even viewed the place in Summer 2015 which is stunning and costs over 150k. My mum is difficult to trust because she doesn't actually have proof or know anything. My dad is also difficult to trust due to his history of lies. All the things they promise seem too good to be true and it drives me insane to be teased about a lavish lifestyle while living in a council flat and previously being on a homeless list. I want to know how I can find out the truth. I've asked for evidence and that resulted in my mum yelling at me, saying I should trust them more and have faith. My dad just doesn't really respond or says "we'll update you when we find out more". All these empty promises are driving me crazy and though I know I should just not focus on them and focus on my own life, it's difficult when my mum constantly reminds me about the flat and how she can't wait for me to have it and that we're gonna go on a massive shopping spree when we get the money. I need to know the truth. I have seen a paper of the flat owners accepting our offer in my dad's name but I need more. Recently he was diagnosed with a malignant brain tumor which has made everything so difficult. Even the general practitioner accused him of lying about his cancer, saying he should be ashamed of himself. This hurt a lot, I shaved my dad's hair when it started falling out in clumps. But the doctor hadn't received his medical records yet and when they later came in she then offered an apology. We since changed practices. However I still need to find out the truth. I'm not the brightest human being and I've no idea where to start. I don't fully understand the situation myself and I'm not sure if it's even possible to find out the truth. I just really want and need it. What should I do? Is there anything I can do, anyone I can call? Apologies for the lengthy explanation. (This is just the tip of the iceberg that is the shit storm of my life).

Thanks for the reply, it's nice to be heard by ears other than my family. I started a Nursing course at university this year but due to poor health I missed a bit and they advised I should take the year out to get better (I had to have two operations on my legs and was unable to walk for some time). Right now I'm living off of my parents and looking for part time work. My mental health has plummeted and I struggle a bit to stay on the positive side and walking can be painful. The only adult I can think of is my friend's father who has been incredible at helping me out. He doesn't understand my parents and isn't totally happy with the environment I'm in. There's only so much he can do though. My friend is a year older than me and wants to help me find out the truth. I've never counted on what they've promised as shit like this has happened my whole life but still, if he could lie about something like this, why? What would be the purpose? Thanks again for your advice.