You percentages are solid for verbal. It seems that you understand the concepts involved. But, since you have difficulty in the last part of your practice test sessions, then there are a few issues to discuss.
Problem #1: EndurancePerhaps you are running out of energy in the last part of the test. It's difficult to maintain concentration for multiple hours. For non-native level English speakers, the verbal section is quite a challenge, since it's a foreign language and comes after the AWA and quant portions. You already expend a great deal of effort on those sections.
One way to deal with this is to take advantage of the allowed breaks. During this time, get out of the chair, stretch, take deep breaths, eat something, and go to the bathroom. In other words, loosen up! Also, I always made it a habit to look away from the screen and take a deep breath every time I moved on to the next question. This will reduce eye and neck strain, as well as provide your brain with oxygen.
When practicing, you need to mimic actual test conditions as much as possible. Don't do
OG questions lying down on the bed or on a nice, comfy chair with the TV on. Use scratch paper (or Manhattan's Test Simulation Booklet) and sit in a computer chair. You can even position the
OG book vertically as if it were on the computer screen. You need to be completely comfortable, relaxed, and used to these conditions to stay focused during the real test.
And do your best to stay consistent. You can't effectively make up the time lost on a question by going too fast on others. There's nothing wrong with finishing a question quickly if you can, but if a question is simply taking too long, then you need to guess and move on.
Problem #2: TimingSimply put, if you can't answer the questions in time, then your GMAT score will suffer. Once you have the concepts under control, you must time yourself and mimic test conditions. If a question takes longer than two minutes (or 2.5 minutes for very hard ones), then you must repeat the problem later. And make sure that there are no distractions or background noise while you practice.
Problem #3: Panic and FrustrationThe last thing that you want to do is panic, because at that point you will not be able to do what you want to: perform well on the test. If you address the previous two issues, this will minimize the chance of panicking, but some people are just prone to do so. Just remember that you are indeed in control. If a question seems insurmountable even after some effort, move on. If you need to take a few seconds to gather your thoughts, then do so. The GMAT doesn't just test you on essays, quant, and verbal. It also tests your ability to perform under pressure. It's just another problem that you need to solve, except that you already have the answer to it.
Based on your response, I can't answer specifically. But I think that the suggestions above should help at least partially. We're only talking ten more questions here. If you can do the AWA, all of the quant, and all but the last ten questions on verbal, then you're very close to the end.