I think it's great to give your letter writers a copy of your LOR if you have it done in time. I was a little slow to write mine, so I ended up waiting really long to give it to them and then had to bug them to finish the letters fast. So give it if you can, or even a rough draft that gives them some ideas about why you're choosing optometry. I also gave mine a copy of my resume. I agree - some of them won't really know what to write about, so the more you can give them the better. You can even offer up getting them a copy of your transcript if that would make them feel more confident asserting how wonderful of a student you are 🙂
I think that's a great plan for the timing of the exam. Even though I took the Kaplan course earlier, I didn't really even return to any of the material until June or July...I did nothing with it in the months in between. I was also taking summer classes like you (Organic Chem and Physics - eek!). Personally, I'm a huge advocate for the Kaplan course. It made a massive difference for me. I was taking a lot of the pre-req's through the time I was studying for it, so that certainly was a part of the boost in my score, but my pre-Kaplan, post-Kaplan score boost overall was about 100 points (pretty big difference!). Like I said, I'm not sure that I got a whole lot from the classroom part. The strategy for the reading section definitely helped. I skipped the math day, so I couldn't tell you on that one. The science days were good, but you're really only able to cover enough material in the class that will help you on a few questions per section...there's just SO much information. It's been about a year since my course, so I don't remember too well what we covered for each section. But the bottom line is that you can't get the other materials (books and online stuff) without paying for the classroom course. The other materials are where the goldmine is (although I certainly wouldn't recommend skipping the class - every little bit helps).
The two important on-paper resources you get are the Lesson Book and the Flashcards. I mostly just memorized the flashcards for biology, chemistry, and physics (I should've for Orgo too...but I struggled with that section most of all). I did them over and over again, mixed them up, and did them more. That helped a ton, because I saw lots of recall facts on the exam from those flashcards. I also read the huge Lesson Book (aka The Brick) cover to cover, reading some chapters more than once. The online materials Kaplan has are amazing. You get 5 full-length practice tests (you're supposed to take them during the course of your class - but if you can get an extension to keep those until August, I would really save them. Take the diagnostic one at the beginning of the course to get your baseline, then save the others until closer to the test when you really have the time to put into studying in between each of them). I think it helps to save them to closer to the test, because I do better retaining the information in the short-term leading up to the test. You also get Section Tests and Subject Tests. The Subject Tests are like short quizzes that are really tough and often go beyond what you will see on the OAT but make sure you really know the material thoroughly - you can take them as many times as you want and I often returned and took them again and again each week just to make sure I retained everything. I did those as I finished reading the respective sections in the Lesson Book. The Section tests are like full-length tests for each separate section - so full length Natural Science, full length reading, etc. You can only take each one once. But they are isolated - so you just do one section of the test at a time. When you do the full-length exams, you can't pause them and return later - you have to sit down and take the whole 3 hour thing at one time. Once you take an exam, that's it and you can't ever retake it - so use your 5 wisely! The great thing is that the interface is exactly what you see on the real OAT - so you are super used to it by test day. Some people I talked to didn't even know there was a calculator or periodic table on there they could use and didn't use it on test day...but you get practice using it through the Kaplan tests. I set up a study calendar to cover certain subjects each week and take the tests when I felt like I had prepared well. For everything I missed, I read the explanation for the correct answer. If I saw that I was missing lots on a common theme - let's say, photosynthesis - then I would go back to the Lesson Book and read that chapter again and pull out the appropriate flashcards. I drilled it. And it works! It does take a lot of time. But here's the thing...it will pay off for admissions and for scholarships. I got a $1,000 scholarship from UHCO (that's the only amount they give) for my scores, unknown amount from SCO because I turned that one down before their scholarship committee met - but the dean had called and assured me it would be a really good one, and an extra $3,000 scholarship from Berkeley. Those scholarships are usually based on your OAT and GPA combined...but I think it's good to think about, because that can make up for the cost of the course all together. Plus you know your sciences better, and you get admission to where you want to go! Like I said, I'm a big advocate for OAT prep.
Whew - this is a book! Feel free to private message me when you start your prep work or around the time of your test if you want any other tips! Also, book your OAT appointment as soon as you can so that the dates don't fill up. I had trouble getting times in August, but I didn't try to book it until the summer either.
Good luck!