Yellowing and blotchy leaves sounds like stress. Stress can be caused by a number of things and transplanting is hard on lemon trees. Did you amend the soil when you planted it? If so, with what? Give it time and water it on a regular schedule so that it never dries out too far (conversely, please don't drown it). Do NOT fertilize until you see the start of new growth. (Fertilizer tends to increase the shock.)
I couldn't really see in the pictures, but the curled leaves in the pictures and your description of spiders everywhere sounds a lot like spider mites. Ants crawling into the tree suggest aphids or another "everything is sticky" sort of bug. Bugs will cause yellowing and discoloration as well.
As a start for bugs, wash your plant with insecticidal soap, get all the leaves top and bottom and the whole branches. Follow the container instructions and do it when the sun is NOT on the tree. Otherwise the soap and water will act like a lens and burn the leaves. Then, wait and see what the tree does.