I don't think you're even close to maintaining a dose that will allow you to remain on. Start out on a morning without any meds and take the starting dose, whatever that may be for you. the next day bump it up if it didn't result in an "ON" state. Then when you get an "ON" take notice of how long it lasts. This is your interval. I take 2 of the 25/100 in the morning. Then I take 1 every hour, yup every hour. A little bit in the bloodstream all the time. I am able to be "ON" pretty much all day. By taking the 2 in the morning followed up by the additional one in just an hour give me an overlap. The single sinemet lasts approx. 1 hour in your body. These meds don't work on the typical take 2x a day, 3x a day instructions. You need to find your effective dose that produces an "on" and then your interval or how long this lasts for you. Everyday will be different depending on many factors such as stress, what you eat, how active you are, how well you manage the medication clock, even whether or not you are "constipated".
I do not take the CR because it takes too long to get me up and running. The reason you are doing well in the morning is because the brain can rest and build up a little bit of dopamine at night. Hope this helps you.