Re: cow milk
If you are still nursing your lo in the evenings/nights/mornings, I don't see why you'd need to give formula. Whole milk should be fine.
My lo goes to daycare and I send whole milk with her. When I'm with her, we nurse. The first time I gave her whole milk she spit it out. So I had my caregiver mix some ebm with it, and gradually increased the amt of whole milk. Worked like a charm.
If she is allergic to milk, you could push cheese/yogurt/other high calcium/fat foods instead, and send water like the pp mentioned.
As for your supply, your body should regulate to your feeding schedule. I stopped pumping at work in May and have had no problems with supply.
Bee- proud mama to Maggie, 6/12/06 and Maya, 10/15/08