Hi, I'm sorry to hear about the struggles! Unfortunately nothing in the industry is really taken for granted, even if you think you're the best luck will have a different view. However, I may have some pointers that might help. I spoke with a 20+ year partner at a large city firm (international and just outside the SC), who made it clear that certain processes may actually be a disadvantage when on the outset it seemed necessary. For context, I'm finishing my final year of an LLB, getting absolutely nowhere with applications. Please bear in mind that my advice to you is merely a repetition of what I've been told, and I really don't mean to pour salt on the wound.
Firstly, the advice he gave to me is to throw as many applications as you possibly can into different firms, as moving laterally post qualifications is easier than entering the profession at the top. He recommended 20+ annually. Grades don't particularly matter in the context of minimum entry, some firms are snobbier than others but all seem to accept a range of both 2:1 and 1st level candidates. It is often more down to the personality of the candidate than it is their academic achievement. Try to make your application broad. Given your experience doing multiple specific post grads, you run the risk of appearing too tunneled into a section of the legal profession. This can often leave a sour taste in grad recruitment's mouth because you are requried to sit more than just a corporate law / M&A seat.
Secondly, the main question partners will likely wonder that potentially undermines your otherwise strong application is why didn't you self fund the LPC? Either directly or through the LLM LPC, surely if you wanted to be a lawyer, you would've made every step to qualify ASAP. I was initially considering to do a specialist masters in Arbitration and DR, but was heavily discouraged due to the overwhelming stress of the SQE. Unfortunately the sad reality is that post graduate degrees do little to bridge any gap between theory and profession. In the eyes of a firm, you will have to convince them that your multiple post grads are of more benefit than the practical knowledge you would've otherwise have gained by directly going down the path of qualification. As it stands, you are competing against candidates far younger and far more maleable as a result of their relative inexperience. My point is that it can often come across as delaying the inevitable, especially when stacked onto the GDL, as you have spent a considerable amount of time outside of the legal profession persuing other paths.
Thirdly, please don't feel too discouraged. This path is not an easy one, and you will never be able to guarantee your future in the career. But, resilience and genuine passion for the field really distinguish you from other candidates. You have more professional experience and more academic experience than 90% of other candidates and it is something you need to lean on heavily. Finally, I have friends who were paralegals for 7+ years prior to being offered a seat at the table. They saw second year students recieve the prized TC they had failed to secure 7 years running. You DO have what it takes, it's a matter of serving that on a platter that is shinier than everyone elses. Perhaps an adjustment of expectation is required? Perhaps not. Only you can decide what left you have in you to continue working in the field, and any decision you make is an honourable one that has not been without much contemplation.
Hope this helps, best of luck to you.