You are a Canadian citizen and presumably not a U.S. citizen or permanent resident. As a result, you have no explicit right to enter the U.S. The U.S. may take whatever time it requires to determine whether to admit you to the country or to return you to Canada. The CBP may search your possessions and person to ensure you are not bringing in any prohibited items into the U.S. While the experience was certainly not pleasant, I see nothing in your post that suggests any clear violations of your rights other than perhaps the injury you suffered from the handcuffs. Whether you are entitled to any compensation for that depends on two things: (1) whether the CBP officers were negligent in the manner in which the handcuffs were used and (2) what damages you suffered from the injury, e.g. medical bills, lost wages, pain and suffering, etc. What was the injury you suffered as a result of the handcuffs and what damages resulted from it? You won't win anything for medical bills except what you were personally responsible to pay; what the Canadian national health care system paid is not recoverable by you.

The process for seeking compensation for this is to first make an administrative claim with CBP. You do that using Standard Form 95. The link to the form and the instructions for where to send it are found here: CBP tort claims.

You cannot win more than the amount you set forth in that claim, so it is important to get it right. I suggest you see a U.S. lawyer familiar with the federal tort claims act for help with that. Should the agency deny your claim you will have 6 months to file an action in federal district court. Note that your case will be decided by the judge, not by a jury.

You are unlikely to find a lawyer to take the case on a contingent fee basis (which is where the lawyer fee is a portion of the amount recovered for you) unless you have a reasonably solid case and you have sufficient damages that the lawyers share of it would make it worth the lawyer's time to litigate it for you.

You may ask the CBP to correct any errors about you in its records. You make that as a Privacy Act request. But you will not succeed in getting the records deleted.