I can see the photo and what stands out is not any damage from insects but what looks like damage from too much fertilizer. We call this fertilizer burn. Most potted indoor plants do not need to be fertilized every three weeks with a liquid plant food. Especially in the winter when indoor plants go rather dormant from lack of sunlight. I suggest you not fertilize at all until early summer once you move the plant back outdoors and you see lots of fresh new growth. Then do not use a full strength liquid plant food as avocados are not heavy feeders. I just use one teaspoon of Osmocote around a gallon sized pot and I do this once a year for my avocados. In a cold climate like Chicago it is the short summers that limit the fruit production not a lack of nutrients. You seem to be watering the correct amount and from the color of the leaves I think it is getting enough sunlight. So stop feeding, no more Neem oil and I predict by summer you may have a real avocado or two on your plant. Keep growing, Marianne Binetti