Hello, sorry to hear about your situation, and I really wish I had seen this post before, however, I believe we are not too late. To answer your question, yes, it's still possible to apply to IB Diploma and find schools that don't have an upper age limit. I took a gap year in between, am 18 and doing grade 10, and will graduate IB Diploma at 21, all that on a full ride scholarship. So I don't think it should be impossible for you, if you are capable to explain the gaps in your education, and be a promising student since IB is rigorous and needs you to be extremely mentally fit before the drain. Not to discourage you though, just being more pragmatic and realistic so you make an informed decision.
Since you said you needed an affordable school, I'd firstly say most IB schools are very expensive compared to your local schools, thus you might need scholarships or bursaries, which are mostly open in between August to January, some until April, thus we are really off the grid, but I'd hope if you are a promising student, many schools can make an exception. Another option could be state funded IB schools, I know a few of them that could only cost you around 2000-5000 euros a year, but you'd need to pay rent (you are 20 so i dont think you need to live with a guardian, but you could) as most of them are day schools. So let me know if you are looking to get either scholarships, bursaries or partially state funded private schools that accept international students on student visa as fully stated funded schools don't, unless your parents are willing to move and work there.
But otherwise, you might wanna explore A level schools too, there also scholarships there and since you had a hard time, I'm afraid IB might break you, however, at the end of the day, it's all about what's really best for you and I'll be happy to support. I've been there so I understand, and I'll be glad to help a friend