I feel your overwhelmed soul.
I work full time as a teacher, and sometimes the only time I get to myself is to go to work. It is ironic, but it feels that way sometimes.
At other times, because I work and because I too am a momma with the DD at night while hubby is at work, I feel I never get time alone to myself.
It's the little moments every day that allow you to recharge. The shower. The drive if you happen to do that alone at any time. Sleep.
Go ahead and find a babysitter for the daytime and two times a week for a couple of hours and . . . sleep. The babysitter can take your child to the park.
Or take a nap when the two-year-old takes a nap. That's recharge time for you.
Eight years old is old enough to begin doing some chores, like load the dishwasher. Start the training.
You say your husband makes sure he gets his needs met. It is your duty to make sure you get yours. Go to bed in order to get your eight hours of sleep.
As far as the weekend schedule, I cannot imagine that he is waking the kids up earlier. If you want the same morning schedule, just do it. Tell the kids dad needs extra sleep. Or, you sleep longer, too, and enjoy that. I also can't believe he's telling them not to brush their teeth. Put your foot down and say that the baby needs his nap at the same time every day. Are you referring to bedtime routine? You go to bed, and let him put them to bed. That is exactly what I do the nights hubby is home. That way, I get my rest and hubby gets daddy time of giving baths and reading bedtime stories.
I'm the one who leaves for work before anyone else wakes up, so I have no good tips for that. When it is my turn to do it, I find it excruciating. Kids find transitions hard. They also take longer to do everything. At times, both hubby and I have coats and shoes on and stand at the door and say, "We're leaving for grandma's / the park / wherever. Bye." That seems to hurry up DD.
I have but one DD, and I imagine the kids feed off of one another, and fight, and complicate things. Perhaps it is time for the older ones to be responsible for getting the youngest one ready? For at least some of the needs? Perhaps you can start routines of songs for transition times that everyone sings, or helps the baby sing? A lot of pre-K and K teachers do that.
We also have family time on the weekends. We make a point to go to the park or elsewhere together for a minimum of two hours, sometimes five. It is sacred time for us. Can hubby and you agree to that? (My complication for this is sometimes I need to check papers).
For us, the projects come last. Perhaps hubby can have apprentices for his projects. That way, your children also learn a skill and get special time with daddy.
I don't get "project time" in my own life, unless it involves DD as well. The most I can manage is to sneak off and take a walk once in a blue moon. At times, I revel in going to the grocery store--alone!
You need more sleep and a small amount of alone time. You can do that. And everyone will be happier.
Best wishes.