Oh no! I'm so sorry to hear that. What a complete bump in the road.
I can give you suggestions to boost calories to help you put on weight. I am in the UK, so I'll try to stick to foods that I believe are available where you are. Please ask me if you're not sure of something and I'll try to find it for you. It's great that you're using protein powder into your smoothies, as the extra protein will help your body heal. My dietitian told me to aim for 100g of protein a day.
If you can get hold of Ensure plus and Ensure Juice plus, each bottle will give you 300 calories per bottle. When I was on rads I made smoothies with 2 Ensure and then I added things to do it to boost. For example, 2 banana Ensure, 1 frozen banana, 1 tbsp chia seeds, portion of protein powder, 1 vanilla protein yogurt and some toasted oats blitzed with ice is really hearty and has great calories and lots of protein.
A chocolate Ensure plus, an orange Ensure juice plus, 1tbsp chia seeds, 2 scoops chocolate ice cream, flesh of an orange, a portion of protein powder and some whole milk in case of it being too thick gives you a lovely chocolate orange smoothie.
A vanilla Ensure, a lime Ensure juice, protein powder, 3 ginger biscuits, vanilla protein yogurt, whole milk and ice give you a great key lime pie smoothie.
There are more food ideas here
and I posted some soup recipes here
which might help you put on weight.
I've even been slicing up protein bars to add to my smoothies. The best one I made had 75g of protein in and was around 800 calories.