HELP: Not Much Improvement After Two Months of Practice

I have been practicing GMAT problems for about two months now and planning to retake the GMAT in mid April. My first GMAT was bad (550 Q47 V20, debrief here).

I participated in the MGMAT Post Exam Evaluation. The instructor told me to focus on reading first and possibly on AWA. Since I did not carefully study OG the first time, I decided to study OG as well.

I started reading books from the gmatclub reading list. I finished The Great Gatsby, Of Mice and Men, The Grapes of Wrath, Thinking, Fast and Slow, Welcome to Your Child’s Brain. Every morning I practiced 5 CR, 5 SC and 1 RC Passage from OG 12, OG Verbal 2, OG 11 and OG 10. In the evening, I reviewed the problems and read books.

I took the MGMAT CAT 5 on Sunday and scored 680 Q48 V35. Obviously it’s a bit of improvement. If I compare to the original GMAT (550 Q47 V20) it’s a HUGE improvement. However, if I compare to the last MGMAT score (670 Q48 V33), it’s just a mere 10 points improvement and 2 points improvement for verbal.

I am worried. Because, MGMAT CAT 5 and 6 are considered the easier ones. Since I performed well before and ended up scoring bad in the real exam, I am worried that I might do the same again!

When I looked into the individual question types, I found that I am still weak in
CR
Weaken Conclusion
Find Assumption
Strengthen Conclusion

RC
Interference
Specific Details

SC
Parallelism
Quantifiers
Modifiers
S-V
Idioms

These are the exact same topic I was weak before!

I am quite dumbfounded and frustrated now! When I crammed it turned out bad. Now I did not cram, still I am not seeing much improvement!

What should I do now?