ah, there's the issue--time.
essentially, you have to change your time/expectation ratios.
at this point, you expect it to take to get out the door is not the time it takes. it feels rushed, and overwhelming and leads to snap (and therefore often poor) decisions (such as DD's snacks) that have outcomes that you're not considering when you make that decision (messy car).
this means that you need to change expectations, and with that, you will allow yourself time to do the things that you need to do to effectively get out the door and effectively maintain your car, your schedule for yourself and your daughter.
in our household, my DH and I could get out the door in 30 minutes. I am usually ready in 15 because i am more organized than my husband.
when we had the baby, i added 30 minutes of time to our morning. DH would take his normal 30 minutes, and i would use that time to get the baby ready. this meant that i got up 15 minutes earlier to get myself ready. then, we were ready to leave at the same time as before, and there was no rush.
it also helps for me to think about my values.
i value a clean car;
i value getting out on time;
i value being clean, dressed, organized, and so on;
i value my son not feeling stressed;
i value not feeling stressed myself;
when you know your values, it's easy to align with them.
so, say you value your car not being messy. what sorts of things can you do to support those values?
one is to assert certain behavior such as no messy snacks in the car. another is to organize what you do in the car in a way that makes sense. for example, when i was in law school, my car was my "mobile office." in the trunk, i kept a bin that had all of my books, notebooks, pens, and a book bag. i had a second bin that held my athletic gear (swimming, running, and yoga) and a bag for carrying that.
i would leave the house at 6:30 am every morning, drive 45 minutes to the school, do my swim/bike/run, go to school, do another workout in the evening, and head home. once home, i would unload the gear bin (dirty duds out) using the bag, and then i would only have to bring that and my lunch out in the morning. and, i would pack that bag and lunch at night so it was no worries in the morning.
i also never studied at home as a policy. of course, this doesn't work for everyone. but, it worked for me. i was at the law school from 9:30 am until 4:30 pm and i would take my classes and study during that time. i was usually home around 7 (after work outs and all) and DH and i would have dinner. I would then rest, clean up, and gear up for the next day.
It is similar now. I know what i'm doing tomorrow, for instance. i know that i need to pack the following items to do that tomorrow. i know that i need to get up at this time. and i know what i am wearing. this way, tomorrow morning will run smoothly. we will leave on time. no stress, no mess. easy done.
so, start thinking about your values and your time, how you can arrange things so tha they are easiest for you. then you will feel more relaxed and everything will get done.