I totally understand that 10 years into this the absolute last thing you want to hear is "Get a beginners' textbook and start from Chapter 1", but in all sincerity and without meaning to be insulting that is what I would recommend. You would probably be able to race through it much faster than an actual beginner, but your grasp of grammar is such that I think you would really benefit from going back to square one and going through filling in gaps in your knowledge and correcting things which osmosis have left you with a mistaken or inadequate grasp of.