I'll let Elizabeth answer this completely, but I hope you don't mind me cutting in
Your BMI is 21 which basically just means your at a healthy weight - but honestly, BMI means squat unless you need it to tell you you're morbidly obese ... (a better measure of healthy weight is body composition / body fat %)
Your eating times look good to me. Not sure how early you go to bed but I know I'd die without an evening snack - so long without eating. Are you doing that because of IBS or another condition, or is that for weight loss/gain purposes? If so it's not such a good idea (your body doesn't want to go that long without energy).
As for post-w/o (weight training, I'm assuming you mean?) - yup, you need carbs to spike your insulin. Not too too much and make sure you're having some protein, but it's crucial to get some fast-acting carbs into you post-workout.
And macronutrient ratio - just a note that many people with IBS on these boards find it safer to go even lower than 20% on the fat - i.e. 10-15% (there is a very recent discussion here on the fitness boards about that). But everyone is different as to how much fat they can tolerate - some can tolerate the full 20%. And if you are weight training you need more PROTEIN than 20% - you should go with something more around 30%. Or even better, calculate it to your bodyweight: 0.8-1g of protein per pound of bodyweight. So for you, that'd be 108-135g of protein a day -- work up to that though since you're still working on getting your calories up (good for you, by the way!). For now, maybe work up to getting your protein intake at around 30% (at EACH meal).
Hope that helps, and sorry again for cutting in