Its pretty clear you had a bad day. Dont worry.
Reaccess the possibility of the goals you had. I think the imbalance is more of a problem than the 620.
Go for the age old way..ABC(BAS in this case

)
Basics
Accuracy
Speed
In that order.
As far as the strategy goes, I believe you haven't found your comfort in balancing accuracy with speed. You need to first start answering questions with at least 90 percent accuracy for a 700 plus score. Once you do this for say 5 tests, then start timing the answering process.
SC-1 to 1.5 min
CR-1 to 1.75 min
RC-1.5 to 2.0 min (including time taken to read the passage)
Then 15 days before exam go backwards...first accuracy and then basic....because by this time you would have trained yourself for speed.
Best of Luck
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