Hey there,

I believe that given your situation, postponing the interview seems to be the smartest choice. This gives you enough time to:

• Focus on quality over quantity. Doing 50+ cases does not mean much if you are not applying the right habits to score high and do a detailed debrief after every case to improve. You want to move from bad to good for your weaknesses and good to great for your strengths --> use the feedback from your previous experience and tailor your prep accordingly
• Consider booking at least an initial coaching session to get a detailed and objective evaluation of your performance + learn the right habits for every case regardless of context and framework + get a tailored preparation plan out of the session that will set you up for an effective and efficient prep. By just reading Case in Point and Victor Cheng, you do not cover the full range of more creative cases that are common nowadays in MBB. Approach > Framework
• Practice drills alone (structure, chart, math) and practice full cases with other excellent candidates that know the right habits and approach. It is crucial that you are practicing with really good peers, otherwise, it's a waste of time. Practicing drills on your own is a huge effectivity and efficiency booster since you can go over many more questions in a shorter amount of time compared to practicing with peers. Do both in parallel!
• For your prep, tailor the cases to the firm you are applying to. BCG cases have some very specific elements to it
• Invest extra time into case math. I have not seen this in your plan. Math is the common most reason why candidates fail. I'd focus 1-2h a day on a. setting up the math logic and b. conducting number drills
• Prepare answers for all the typical fit questions and PEI stories (3-5 hours) and rehearse them a couple of times (5 hours)

If you cannot get an extension, you can still work on the things mentioned above. However, the risk is that it is not enough time to

• upskill from your weaknesses to create solid foundations
• upskill from your strengths to become excellent on certain dimensions
• internalize all the key habits
• get adequate rest periods and you burn out in the process 

All the best with your prep!

 Florian

Cheers,

Florian