First of all thank you for such a detailed describtion, that makes it a lot easier to understand where you are coming from and give potential advice.

With regards to your Quant results I do feel your pain, even though you are already a couple of steps ahead of me.
I can recommend a combination of the Gmatclub test together with the MathRevolution allinone51 course, it is fairly affordable and I have the feeling it is a quite good combination in terms of getting you up to speed in Quant. Furthermore, there is a Gmatclub Math book which gives you a good overview about the various concepts beeing used.
Last but not least there is a topic from the MathRevolution founder in which he talks about the most common topics in the Gmat Quant sectiond and the likelyhood with which you are going to see which style of question.
Ill try to provide the link tomorrow once I have rediscovered that specific thread.
Hope this helps and all the best for your next try mate!
Best regards,
Chris