Hi S.---You don't need cows milk to wean your baby from nursing. This may not be exactly the answer you are looking for in terms of weaning suggestions, but, I am hoping to help relieve some of your anxiety about what to give him to drink. (it's been a LONG time since I've weaned my youngest)
I work with a Naturopath who has her PhD in Nutrition. I've learned that cows milk is not a health food, in fact, it actually causes many problems in the human body. Please explore www.strongbones.org and it's parent website www.pcrm.org. And read The China Study by T Colin Campbell. Also, lots of info at www.notmilk.com (?).
Healthy plant based substitutes include soy, almond, rice and coconut milks. There are others. Just keep trying to see what it is that you and your kids will like. Again I just drink water and use one of the plant milks for cereal, baking, smoothies and even mashed potatoes.
I have great charts that lists calcium content from various food sources. We get more absorbable calcium from green leafy veggies such as broccoli, kale and bok choy and from sesame seeds, almonds and soy that we would ever get from cows milk. At our house, we also use a whole food based supplement (that is available in gummies) that has all of those wonderful greens in it.
But for the weaning, loving persistence and patience is in order. Keep trying. It takes several tries to introduce a new habit. Oh, check out www.askDrSears.com to see if he has any suggestions. I have the honor of working with the Dr. Sears family so I know that they are very astute, conservative and well-loved by their patients.
Good luck. Let us know how it turns out. And, btw, it just may take the seperation for him to realize that now is the time to adjust to life no longer nursing. He may not like it, nor you, but you will all be fine. In health, D.
PS. I'd be honored to help with any other questions you might have about optimal health and nutrition.