My DD had a similar problem with K, though not to this extreme. His hiding of his abilities has somewhat handicapped you in your efforts to get him appropriate differentiation, which can take forever even in the best of circumstances. Considering how strongly this situation is affecting him, and how difficult/long it can be to make this work in a school situation, in your place I'd pull him out of school today and begin homeschooling.
I assume your DH's reason for stating Aidan needs to be in school is for social development. If that's true, it's probably worth pointing out how sending him to a place he hates is unlikely to help him win friends, and that homeschooling now at K does not preclude him going to school later.
Homeschooling a gifted child takes up a lot less of your time than you might think. There's going to be some time for you to shop for materials and plan lessons, but the actual schooling part took my DW less than three hours a day. Aidan won't be wasting his time waiting for other kids to get it, other kids to finish their work, standing in line waiting for other kids to quiet down, etc.
