Read The Hemingses of Monticello by Annette Gordon-Reed for great answers to many of your questions.

Thomas Jefferson treated his slaves, I would argue, better than average, but that is not going to be used to justify Jefferson's use of slavery, or help Jefferson escape the inevitable contradictions easily found when looking at his views written in the Declaration of Independence. Gordon-Reed absolutely reminds the readers in her book not to do this. In fact, Gordon-Reed at times will even suggest that Jefferson's treatment of his slaves may have been an attempt to settle internal guilt within him as a slave owner, which she rightfully shoots down as nonsense as a reason to justify anything. If Jefferson was feeling guilt about owning human beings, he should have freed them. She criticizes Jefferson about this by claiming he acted largely in his own self-interest, preferring to keep slaves over the inconvenience of not owning slaves.

Jefferson did not want his slaves beaten, and he believed that his slaves were generally capable of achievement. He had a slave run his nail business, including handling the money the business collected and he got to keep part of the profits. Jefferson never claimed the wages earned by his slaves, even as he was saddled with extreme debt.

But there is an extreme complication in providing a simple answer to the question, and that is the fact that a large amount of the house slaves at Monticello were his literal family, and he absolutely gave them preferential treatment. They were also mixed race. The Hemmings family came to Jefferson through his wife Martha, and Elizabeth Hemmings was a mixed-race slave that had the children of Martha's father. So, Elizabeth Hemmings was a half-sister to his wife Martha. Elizabeth's decedents comprised of a large amount of the slaves at Monticello proper.

Of course a discussion of the Hemmings family cannot go without mentioning Sally Hemmings and the relationship Jefferson had with her that produced children. All were freed and some even moved on to pass as white in American society.

Jefferson treated the children of Elizabeth pretty well in my opinion. Though Gordon-Reed once again reminds us that slavery was the institution of the time, and that consent for Sally was impossible, and the implications of slavery dominated the lives of James and Robert Hemmings who were both given their freedom after many many years of being slaves to Jefferson. While slaves, both were actually frequently away from both Jefferson and Monticello, and Robert had built a fairly independent life away from Jefferson having a wife and children living in Richmond VA working and earning his own wages which Jefferson never saw the need to collect. They only returned to Monticello when called upon by Jefferson. Jefferson never sold the Hemmings children, outside of one time where Mary Hemmings requested she be sold to a specific man, of which they had many children together. They would occasionally be rented out, but they were to never be sold separated from each other.

James Hemmings became a French chef, trained by a legitimate French chef while Jefferson lived in France and at great expense to Jefferson who was a Francophile.

On the outlying farms Jefferson owned, life as a slave would have been fairly typical of being a slave elsewhere, except Jefferson treated his slaves with more respect. Beatings would have been rare, and the buying and selling of slaves was much more open when compared to that of the Hemmings.

As for his views toward his children's skills and that of Elizabeth's decedents, Jefferson was a product of his time, and largely trained his slaves into the gender roles of the time. Women would learn how to weave and manage textiles and men would be carpenters, or for example, manage his nail business.