Hi Callum and welcome to RYL. Looks like a tough situation you're in but it's good to see that you recognise you're in a spiral and want to change it - that's a major first step.
A great way to get references, skills and qualifications that will help when you don't have loads of academic qualifications is to volunteer. It won't help with the 'helping your parents' stuff straight away of course, but it gives you something to put on your CV, gets you involved with and meeting other people and gives you a sense of importance and value.
So perhaps finding a project / volunteering position locally might be a good way of moving in the right direction? Idealy doing something you are passionate about, but that might not be possible depending on what's on offer around you. Either way, it will be a very positive thing and will give you experience to put down on CVs, skills and challenges you can talk about in intervews and a lot more besides.
In the long term, don't stress about lots of academic qualifications - it really is not the most important thing, trust me. Learn about the things you love, focus on things you are find you are good at and the rest with come in time, with or without a glowing school career!
No easy instant answers of course, but I hope that helps just a little bit