I had a 183 PSAT and pulled myself up to a 2130. Improvement is possible. I highly recommend Princeton Review, Gruber and Barrons books. Barrons SAT 2400, Barrons SAT Critical Reading Workbook, Princeton Review Power Vocab and Grubers Critical Reading Workbook. They helped me pull my scores up and get my stuff together.
For math, you just have to know the concepts and remember them. It’s important to not get tricked when you’re in the room and go for the Joe Bloggs answer. Math was my hardest to pull up but I managed.
CR was my weakness. Went from 59 PSAT to 760 SAT. You have to go with a strategy that works for you. I read the passages and then go to the questions. I remembered definitions obviously (not like flash card memorization) but like actually knowing what bellicose means. If you don’t know a definition, work off the ones you do know and go from there for POE (process of elimination)
For writing, it’s basic English. Know your idioms and don’t be tricked.
Don’t worry about timing yourself just yet. Familiarize yourself with the questions and the format. Then worry about timing. Don’t underestimate the essay either. It affects your writing score. About finding time for studying, focus about an hour a day to start. Either in the morning, afternoon, or evening. Doesn’t matter, just focus some time on it.