Not much you can do besides keep up the studying until the test and just hard focus those problem areas. What trips me up a lot on reading and grammar is usually trying to figure out readings for kanji and going too in depth with the analysis. During the actual test, I’d recommend going through those problem areas once quickly, then doubling back afterwards to see if you can spot anything new or take a bit more time to think. That way you’ll be able to answer every question where even a random guess is 25% chance to be correct. Plus, you’ll likely be making educated guesses anyways so it’s more like 50-60%.
And btw, those aren’t bad scores for a practice exam. Keep in mind that N2 is only the two sections instead of three, so you can still pass even if you bomb the reading portion iirc. That being said, probably best to practice it more before the test anyways :)