Another LP working full time here. I do a 45 hour week.
My STBEXH takes DS every other weekend. I use that time to do a huge shop, stock up the freezer and make soups and meals for the evenings and blitz a few rooms.
Use your lunch hour in work to online shop if you can. You could also go out for a run/gym or swim a few times in the lunch hour If possible? I also pop out if I can for a wax, treatment, haircut if desperate.
I get up at 6am, hang out the washing, put in another load and shower etc I have a robovac that I put on and leave to run before work. I empty the dishwasher from the previous evening while DS eats breakfast.
Clothes ready the night before is a timesaver indeed.
I use the train journey to answer emails and do some organisation. Google calendar is a godsend for activity reminders etc
Keep a couple of loaves and some milk in the freezer. You always realise you’ve run out at 9pm at night! 
I watch Netflix whilst ironing in the evening. And if I watch TV I get up in every commercial break to do something. It’s stealth tidying.
And he kind to yourself. That’s the most important thing.