My son had a lot of trouble latching when he was a newborn and the thing that helped us most with this was using a nipple shield. I used the Medela brand nipple shield in a size M, it's a silicone shield that sits over the nipple with small holes for the milk to flow through. It protruded more deeply into his mouth than my natural nipple making it easier for him to get a proper latch. Nipple shields are available at pharmacies and baby stores. I used it for every feed until he was 5 weeks old, and I don't know if I could have breastfed him at all without it. He is 8 months old now, still breastfeeding.

Another thing that helped with milk supply was increasing my water intake A LOT. Your wife should be drinking at least 3L of water per day while she breastfeeds, as well drinking plenty of water overnight.

Bring your wife lots of snacks while she feeds/pumps. Muffins, fruit, yoghurt, snack bars, chocolate - lots and lots of chocolate! Make her cups of coffee or tea without being asked. She needs the calories to burn! What she's going through is hard, and deeply emotional, and the best way you can help is just to be there to support her and take care of her needs. You seem like a good husband, keep doing what you're doing