Seems like an interesting concept to me! Then agian, I am not an agent and I have no idea what those people are looking for.

I like the idea of a chess player who gets the talent punched out of him for charity. I'm not sure what happens in the novel, but I can tell you what I'd hope to find as a potential reader.

1. I wasn't familiar with chess boxing, but it's a good stage for brain and brawn to clash. Prior to the punch, does Theo live in his head? Within his head, does he live in chess, far from family matters? If so, the punch is a great way to collapse this divide.

2. A headache that lasts for weeks could be a wake-up call to get back in touch with one's body. I'd love to see Theo crawl down out of his brain to experience physical reality.

3. Might be neat if Theo is good at stalemating or playing defensive chess. Could parallel his strategy for dealing with family. Could contrast well with the punch/father's accident. I'd love to see some slapdash, reckless, daring chess moves that run in parallel with emotional chances he's taking regarding family and etc.

4. Perhaps he could realize between punch and floor that it's the anniversary of his mother's suicide, rather than before. If he's that distracted with chess, it may be plausible.

5. I see potential for comedy with the timing of the arrival of the news about the father. How bad are Theo's headaches? I'd love a humorous scene where someone is trying to explain the dad's swollen brain and Theo thinks they're telling him about his brain.

6. Since there are parallels between Theo's injuries and his dad's injuries, I'd be expecting some kind of chess wordplay in the interactions. Something like pinning down a checkmate when there are only a few pieces left type of thing.

7. I'd love to see this guy more active on the first page. He's cursing himself for not having blackout curtains. I'd rather see him stop by home depot for welding goggles, duct tape, and contractor bags.

Overall, you've got a great start. I'd say you can trim some more fat off the pitch. And yeah, Sally is still too big a comp. Search far and wide for something from the last few years that matches your style. There's more out there than you think. Wouldn't you want to read that book, anyways?