I was in a very similar situation recently.
I decided at the start of the P level papers that I did not want to be an accountant for much longer. I wondered whether stopping and going on to my new ambition (teaching) was the best decision for me. I decided to finish the ACCA in order to have something to prove to myself that all the effort and time spent on the exams already done did not go to waste. Plus, being a qualified accountant will give me more credibility as a teacher when it comes to guidance and offering careers advice. See - an indirect benefit of finishing it.
However, you need to guage if you have enough will-power to do the last three P2, and the options. Those three are by far the hardest of the ACCA examinations and will be the steepest part. If you don't have the energy to do it anymore, then it may be better to stop now. There were so many times I was frustrated and angry because I found these three so difficult. And it is a huge sacrifice as far as free time goes.
I just found out that I passed the last two exams so I am done and still plan on becoming a Maths teacher in about a year's time.
So if you have the determination and think you can do it, then do so even if you won't be an accountant anymore. Having something to show for it will make a difference even if just for yourself. But if your energy levels are spent and you don't have anymore juice, then it may not be worth the frustration.