In my fictional country (a dictatorship), the social structure is very rigid. A complex system of classes, sub-classes, castes and professional groups exists, with little or no social mobility. The lower classes have no access to higher education (or even decent vocational training) and are constantly monitored by the police.
As already implied, every social class is separated into a subsystem of groupings that is even more complex that the system of classes itself, meaning that even the dirtiest proletarians and asocials have somebody to look down upon.
On the very bottom of the population pyramid, two groups, both damned to a short, hard life of menial work and unfreedom, exist. Let's call them serfs and slaves, the former standing higher than the latter.
Serfs are legally bound to their owner like slaves and receive no or little salary. They are most commonly found in the country, working on farms for dozens of generations. In the rare case serfs are transferred to or born in a city, they work in factories as skilled laborers, having some responsibility, usually as a supervisor over slaves. Their children are usually allowed four years of education. In rural environments, especially on very small farms where the serf-owner relationship persists for centuries, serfs are treated as a part of the family and sometimes live and eat together with their masters. Serfs working in the household usually are butlers, maidservants and cleaning ladies; senior serfs can become personal secretaries. Universities utilize serfs as laboratory workers. Owners can send serfs to the military (effectively the military rents them), receiving a large part of their pay; such serfs usually serve in the line infantry. Serf families who receive salaries usually save them (over the course of multiple lifetimes); they can buy themselves free with the permission of their masters and the local magistrate to become free laborers (often becoming wage slaves in large cities). Vice versa, free laborers can voluntarily sell themselves into serfdom in return for accomodation, food and safety. The process of the direct transfer of a serf between owners is somewhat bureaucratic.
Slaves are classified as cattle legally. They perform the dirtiest, most menial and excruciating labors and are considered to be expendable. They have no hope of freedom. They receive no education or training whatsnotever (and can usually not even speak properly) except for what is required for the execution of the job. Slaves are usually not rented but bought by the military, serving as poorly armed or unarmed cannon meat or test subjects (e.g. roles that bear little chance of survival). Mind control implants, drugs and draconic punishments are used to keep slaves submissive. Slaves may be easily traded on slave markets and auctions, serving as tokens of bulk payment and speculation objects. Slaves are usually supervised by serfs, who treat them extremely sadistically.
My question is:
Have both terms been, with historic usages in mind, chosen appropriately and can they be used safely without causing much confusion to the reader?