your plan sounds fine. devote some time to practise probability and statistics problems. also, time yourself when your practise with a set of problems. see how you do under time constraints.
I dont know if you have thought of keeping a log of your errors or new concepts that you learn.
every time ,you learn a new concept or make an error , write it down somewhere. everytime your start your prep, always begin with the problems or the concepts in this error log
. if you do this regularly, i am sure you will improve with time. practise will not make a difference if we keep repeating errors.
we also have a great resource of problems on the GMAT forums. go over 10-15 of these tough problems every day and i am sure you will see a difference in your prep.