I like Jonathan's advice in general.
Here's a link to a post in which I discuss inference questions: viewtopic.php?f=9&t=3847&hilit=pets+favorite+allergic
See if that helps you any more. It's good to also have a backup plan (another way to eliminate wrong answers) for any question type, especially on verbal, so keep developing that skill.
It typically takes between 2 and 4 weeks of regular practice (almost every day) for people to get fast with diagramming. Have you been doing it that long yet? I like Jonathan's advice to review your diagrams after you've finished the problem. Also, keep this in mind: the diagram is about helping you to understand what's going on. The diagram is NOT about taking notes that you will use at some later time. You're only going to spend about 2 minutes on this question, so you can keep a lot of the little details in your short-term memory. You can also abbreviate heavily - stuff that you would never abbreviate if you were taking notes in school - because you'll remember the abbreviations for 2 minutes (and after 2 minutes, it doesn't matter if you forget). Instead, concentrate on the main flow of information in the argument - what's the conclusion? what evidence does the author use to support that conclusion? does the author offer a countering point of view? if so, what is it? etc.
You still need to figure out which verbal questions are costing you too much time and let those go too. For instance, you mention averaging closer to 2:30 on CR. Are there certain types that you're more likely to get wrong even when you spend 2:30? Most likely there are. Do you know which types they are and how to identify them so you can decide to get them wrong in 1:30 instead of 2:30? Sometimes, that's literally the choice you're making - not how to get it right, because you're not going to get it right, but how long you're going to take to get it wrong. So get it wrong faster. :)
It's not unusual to feel a bit burned out. When that happens, try taking a day off and doing something you find fun and relaxing instead of studying. Your brain will be much better able to learn when you get back to studying the next day.