He did have Scoliosis which is an abnormal sideways curvature of the spine. Under most circumstances this would not be noticeable, especially when fully clothed or in armour. It would have been noticeable when his naked body was slung over the back of a horse, after Bosworth, which is probably where the hunchback myth started in the first place.
Richard didn’t “usurp” the throne.
He did accept when he was offered it by the three estates of the realm, the Lords Temporal and Spiritual, as well as the commons.
Richard wasn’t planning to marry his niece Elizabeth.
He was in negotiations to marry the Portuguese Princess Joana. His diplomats in Portugal were also seeking to arrange a second marriage there – between Elizabeth, and a member of the Portuguese royal family (who did become King!).
Richard didn’t kill his brother George, Duke of Clarence.
He did try to save his life by appealing to Edward IV, who had found him guilty of treason.
Richard didn’t fight at the first battle of St Albans, when he was two years old (as was proposed by Shakespeare)!
He did fight at the battles of Barnet and Tewkesbury, when he was a very mature 17 years of age.
He didn’t have William, Lord Hastings killed without due process.
As High Constable of England, he did hold a trial, convict and sentence the man in the same day. Many times Richard had shown restraint in such matters and had been more lenient than many men of his time.
And lastly, you may be surprised to know…
As Lord Protector, he was not the personal bodyguard to the heir apparent after Edward IV’s death.
He was responsible for the welfare and security of the state and when he saw a legitimate threat to the realm’s security during the Spring of 1483 he had to act to protect the nation from the illegal seizure of its navy and treasury.