I am dealing with a very similar situation. My son is a lot like yours. The only thing he doesn't do is cry He's not terribly emotional but I would also say my son's tantrums are worse. A 7 yr old should not be throwing himself down on the ground and screaming, "I want a new mommy" because I won't let him have his way. Or, kicking the door! I'm not unreasonable with him but responsibilities first! My son has not had an IQ test but I'd love to have him take one. He has been diagnosed with ADHD (and has some symptoms of Asperger's but not enough) but I'm not convinced this is the problem. Many people have told me he is so smart and should be in the gifted program at school. ...but he's not. In fact, he's quite mediocre in the classroom. I guess this is why he can't qualify. You probably need to have stellar grades before that can happen. He's definitely a little different. Not your typical kid. He has the mind of an engineer. He's also EXTREMELY strong willed and stubborn. He has a sense of entitlement (not as bad at school as it is at home) and is terribly jealous of his younger sibling.
So, other than the fact that he is gifted, I would be willing to bet your son struggles with anxiety! I know mine has always struggled with it. Talk to your doctor about that. I'm sure there is something he can suggest. Maybe start by treating him with some natural products. If that doesn't work, maybe you can toy with some sort of medication over the summer (I know that sounds really scary). I hate the idea of medicating a child but maybe it's necessary. I think I would rather take the risk of medicating than watch my son be bullied. I think constant bullying is worse. You should make an appointment with the school counselor. Maybe she can help. Ask if there's some sort of mentor program where your son can mentor a kindergartener. He needs to feel in charge of something in his life.
I don't know where Troy is but do you have charter schools in the area? I would try to enroll him. They are often great for kids like ours; I have toyed around with this idea for my son. Kids like ours have brains that work differently than ours. They are smarter but unfortunately the social part of their brains are wired a little differently and they seem to not fit in with the rest of our "average" society. When you encounter problems like him skipping the problem on the math test, fight the urge to be frustrated with him. His brain probably sees this as stupid and redundant and he's not going to do something stupid. An average kid does what they are supposed to do but these guys don't get it. We will have to teach them over and over what society expects of us, even if it is stupid. Just tell him, you're right, that is silly but we just have to do it because some kids don't realize that 2x4 and 4x2 are exactly the same thing and they have to be taught....you already know it. However, you have to finish it or the teacher will mark it wrong. What seems so natural to us, they have to be taught through repetition.
I know this is probably going to be really hard but I'd get him off the school bus or demand that he sit with one of your older kids to protect him. Do whatever you have to do to protect him from the bullying. Maybe the counselor can give him something else to do during recess (like sitting in with a kinder kid to help him read or practice math) or let him eat lunch elsewhere. My son feels so empowered when he's teaching those younger than he is. When he does this with his little sister, I see a whole new side of him (a happy and secure one). I'm not sure doing this is the best thing to do but I have NO TOLERANCE for teasing others, it will effect his life negatively. Try to find a group of kids in your area that he's like. That's what I am in the process of. Not easy but I'm looking at engineering camps and such. I know these kids exist! ...even though I feel so alone sometimes.
I'm getting long winded, sorry. So, start working on the anxiety!!!! There's no other explanation, if he's obsessing about things he cannot control like college and his grand-dad at his wedding. Lastly, take him out of that school, if you have to. And...know that you are not alone! I have met others struggling with this too. It's been a slow process but it's happening and I'm making it a point for my son to meet these kids.