I've reached level 60, but I feel the need to restart

Since you mentioned that writing is one of your weak points, I would recommend practicing that. A good app for that is Ringotan, it’s for andriod and recently became available for iOS too. It’s an SRS system for writing and you can set it to follow WK order. The advantage to that is while practicing writing, if you come across any kanji you don’t recognize, you’ll know it’s something you learned in WK and can resurrect it to refresh your memory.