I had forgotten about Frodo also "being his own master" as the phrase goes. I
guess I took Tom's obvious uniqueness to prove his uniqueness. A little too
much straw in the foundation of my argument.
But I do think that, like Elessar, Tom takes responsibility for his "little
country", as least as far as protecting visitors from harm; and I can't believe
he would sit idly by if Black Riders entered his land. He is "no master" of
them on the Road to Bree, as we know, and so refuses to escort the hobbits
there. But is he really helpless against them in the Vale of the Withywindle or
on the Downs? He has no fear, after all.
I am also still intrigued by my thought that Tom does not owe the Valar
service, in your second sense, as do Frodo by your example, and presumably all
other creatures on
Middle-earth.

"Wake up and smell the coffee."
squire online:
Footerama: "Tolkien would have LOVED it!" (improved!)
The Valaquenta discussion