I see nothing nihilist in your beliefs. They are simply existential.

Meaning of a word can be found in a dictionary that records accepted usages.

From one google search Oxford dictionary:
Life: the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death.

Moral are objective observation of a person's behavior with knowledge of good and evil and arbitrary rules.

You lost me at existential nihilist.

If you have not read it you may find La Nausea by Jean Paul Sartre an interesting novel.

After rejecting the concept of a deity, I made the conscious choice decades ago to "believe" in the pursuit of the well-being of Humanity, the biosphere and life in general. This included support for the U.N., the E.U., "Open Societies" and open borders. Then, the Arab Spring occurred, precipitating mass immigration into Europe and the rest of the world from the Middle East. After a few months it became apparent that my "liberal" (leftist) viewpoints were supporting the propagation of the cruel, oppressive, imperialist ideology of Islam.

While remaining a "classical liberal", I now support nationalism and patriotism. If leftism comes to grips with and addresses the scourge of imperialist Islam, I might resume my leftist viewpoints. Islam has achieved a Darwinist life of its own, independent of its followers, whom it "uses up" in support of its own propagation.

Each human has the right to pursue a meaningful life. This includes the followers of "the prophet", who are oppressed, betrayed and enslaved by their indoctrinated ideology. My approach is to hate the ideology, but to love the followers. We need to help and encourage the followers of Islam to apostatize, freeing themselves and humanity from the evil disaster of Islam.

Apologies to @AtheistForLife for my redirection of your excellent post.

You say you have selected secular humanist ethics and liberal secular ethics as your primary human value system.
Can you state a reason for your having done so?

You: “I follow secular humanist ethics and liberal secular ethics, not because I view them as an absolute, objective morality for all humans everywhere on this planet, but because I have selected them as my primary human value system.”

Also You: “I also don't think that we have free will, just based on what we know about our brains.”

If you don’t have free will, who or what did the selecting? If it was selected for you without your input, how can “People make up their own meaning for life.”? If it is all selected for you, how is that not objective instead of subjective?