Quantity of feed seems low to me too. But within a normal range for your flock.
You don’t live somewhere that can rely on free ranging, for even half their feed, I can’t imagine….unless you specifically plan this. And even then, you are in a colder area, so snow, cold, and lack of bugs will limit the value of free ranging.
However, you have space!! So, do some research on types of plants, grass, greens that are nutritious for the poultry. Encourage bugs to find this area attractive. I know I’ve seen seed mixes (from online resources) that are made for poultry so you can grow a nutritious pasture. I would think that with some research and effort, you can create a nutritious free ranging area for your poultry that helps cut some of your feed costs during the growing months.
Even with free ranging, most people find their birds do best with supplemental commercial feed. I second the idea of letting them eat feed first thing in the day. Cover it up after an hour, if that is possible with your schedule, then re-open 2-3 hours before roost time so they can fill their crops.
FWIW, we are in year 6 of gardening in our current home. It took a good 2-3 years to notice an obvious population boom of insects and worms. But, your efforts will pay off.