I was brestfeeding a 2.5 year old when I got pregnant. My supply dropped around 6 months and he had his first asthma attack and it was very bad. He was in the ICU at a major childrens hospital and nursed enough that I had a lot of milk again. They thought he would have to stay 3 weeks and we went home in less than a week. He continued to nurse along with his baby brother and weaned on his 6th birthday. His allergies and asthma were so bad he needed to breastfeed. Both of my other children had their first asthma attack when they weaned.
Some women can maintain a supply while breastfeeding. It's common for supply to drop a lot around 6 months. That may be after your baby is over 12 months. It would be great if you could have 32 oz a day up to 12 months. There is no perfect way to tell how much your baby is getting. Weighing your baby before and after feeding isn't perfect but it may be the best you could do if you wanted to make sure your baby is getting enough. It is important for brain development that babies get that much. Once your baby is 12 months it isn't supposed to matter if your baby gets breastmilk. If you want you can continue to breastfeed and tandem nurse. Some mothers love it, some put up with it, and some don't like it much but do it because they think it is best for their child.
If your baby isn't getting 32 oz then he should get milk from another mother or formula, not goat's milk or cow's milk. Once your baby reaches 12 months he doesn't need to drink cow's milk. He only needs 2 toddler servings (according to the government) of milk and most toddlers like foods with milk in them like cheese, yogurt, and foods with cheese in them.
Congrats on the new baby! Sometimes stuff happens and we have to do the best we can do.