Original Questions:

1. Only an Eved Canaani may eat of the Kohen's Terumah and not an Eved Ivri. What's the difference?

2. What is the inner message of this Halacha to us in our times?

Final Answer:

The Eved Canaani is in a state of complete submission to his master (in contrast to the Eved Ivri who goes free) and therefore as a complete servant he can partake of the Terumah of his master the Kohen.

The Eved Canaani form of serving Hashem may not involve love and awe of Hashem but in a certain sense it is higher because there is a submission to Hashem even when we are not feeling the love and the awe. In this state we express our complete servitude to Hashem. As the complete servant, totally nullified before Hashem, we use Hashem's world in the way that He wants us to use this world.