1) No need for a retake. OChem isn't that important and even then your score isn't bad or worrisome. . AA of 20 and RC/PAT of over 21 is great! If you have a good science GPA it can convince the schools that your TS score isn't indicative of your scientific genius, but regardless a 19 is good. Great job and congrats!
2) Kaplan gets criticized a lot here mainly because of price. For the amount spent there you can do a lot more elsewhere. Of course Kaplan does offer personalized tutoring etc. which no one else does. If that is what one is looking for (and has the requisite amount of funds), there really is no better option. All I am going to say is, I am glad it worked for you and if others want to take that Kaplan course I wouldn't discourage them from doing so.