I did this as much as possible during the past year and my son seemed to really love it. My son was only in PT daycare (5 mornings a week until 1) but I know what you mean about things getting hectic. You find your peace and beauty where you can. Next fall he starts waldorf kindergarten (yay!).
I really liked "Earthways" and "Toymaking for Children" as well as "you are your child's first teacher" for practical ideas of activities/structure together (and just gloss over the parts that are guilt-inducing). We did a lot with fairy tales and storytelling... he loved to hear me tell the three billy goats gruff and jack and the beanstalk, and I started doing a lot of storytelling while we are on our way to school, when running errands... we also sing together all the time, and those are parts of the "oral tradition" that you can bring into your routine/daily life even when you aren't home.
Here is my advice: don't think about what you do not have time for, but think about how you can consciously fashion your daily life and the time you DO have together around the ideals of simplicity and peace: routine before bed; creative (but simple!) activities to do together in the evenings (even get it set up for the next day right after he goes to bed? I posted a little list of ideas on my fridge that remind me when I am harried to take a few moments to set up watercolors, sewing, blocks, an easy food prep activity, watering the plants, etc); including your son in child-friendly chores and the care of the home (dishwashing, hanging out/sorting laundry, sweeping, etc); and cutting out as much as possible to carve out some unhurried time together when he is not in school... good luck. Its hard to have a FT out of the home job, but you are providing many important things with your work.
Also, your son is only 18 months, so feeding and napping and making sure to include outdoor physical play is really a lot! As he gets older, he will enter into other kinds of more "waldorfy" activities with you with gusto.
dissertating mom to three