Hey,
Well maybe you can try your second test in a physical test center. I have read many such horror stories of the gmat online test from others also. Regarding a study plan, I would say you need very intensive prep as you need to considerable improvement in both your quant and verbal scores, and you have 2 months left. The study plan mainly depends on the resources you use.
The blue book is good but not the best. Also, you need to mainly strengthen your fundamentals before you start practicing hard questions or complex strategies. You can take 2 approaches - book approach or online video approach. For online approach, I would say the TTP course is pretty much the best for quant. Although it is very long and extensive, and it will be difficult to finish the whole quant in 1 month but its still doable. You can also checkout Wizako, they are an Indian company and have online classes and pretty cheap tutor classes also. Also, before you sign up for any course, do take their trial version. This way you can see if the online course is good for you or not. For example, even though TTP is the best, one of my friends said he didn't like it as its was too text heavy for him.
For the book approach (my preference), you can either get the veritas guides or the manhattan guides. The difference in my opinion is the
manhattan prep guides drills more in the fundamentals, whereas the veritas guides covers more on strategy, how to approach the questions and think like the testmaker. The veritas guides have more practice question per topic and are more similar to actual gmat questions. The manhattan guides has limited questions but they advise you to solve particular OG questions along with the books. You can go either way, it doesn't matter much. You can download the free veritas prep app from play store to access all their videos from their on-demand course (was gamechanger for me). Go over each the topic-wise video after finish the chapter. In the end, get the Official guide and the advanced questions book and practice those questions.
For practice test, the best one is obviously from gmac on mba.com, the second best is from
manhattan prep. Veritas prep tests are good as well, but they are much harder than the actual gmat and this can affect your confidence. So I would suggest getting the official tests and the manhattan tests.
Now with regards to a study plan, if you sign up with any online video classes, they will most probably provide you with one. Even if they don't, plan it out in such a manner, wherein your studying of fundamentals (going over the books with topic-wise practice questions or finishing the online course) should be done in the first 5 weeks. The remaining 3 weeks is just practice test, practicing questions from advanced questions book, reviewing your answers and concepts, and just practice. Let me know, if you need any other help

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