Existentialism doesn't necessarily claim that nothing matters, so yours sounds more like optimistic nihilism, which is very similar if not identical to absurdism.
The absurdism depicted isn’t pure absurdism because there’s the presence of style, which is a system of meaning and value. So, as depicted, that’s more existentialism or a healthy and cool blend of absurdism with existentialism.
Sartre says you can be angry and furious at the absurd, Camus says to laugh at it. The absurd is the gap between what we expect to happen, and what actually happens.
Many absurdists also believe in a mind-body split (see Nagel's "What is it like to be a bat?" essay, available for free in pdf format) or that consciousness may be something other than physical and that's where I tend to disagree with them. In general, the essays tend to be extremely interesting and worth reading even if you disagree. Philosophical literature is usually written so precisely and specifically that it's unlike other types of reading.
You can do neither. Knowing that there's no inherent meaning to existence isn't for everyone. And I would argue that it's better to not be a nihilist at all than to be a pessimistic one.
Indeed, I do think the same. What I have trouble understanding, and even with close friends, is how "no inherent meaning to existence" seems to quickly become, in some cases, "no meaning to existence". I always tend to think this slide tends to exclude another possibility. A non-inherent meaning.
Wow it's really hard to pin down a definition of Nihilism. Anyway, I always saw Nihilism as a view that nothing is meaningful, that everything means nothing. But not that nothing matters. If you have no meaning to ascribe value to anything or anyone, you wouldn't find meaning in unnecessary harm or discomfort to others, in a harm reduction mindset.
To me, the definition is "the belief that there is no intrinsic meaning to human existence." You then have two choices: despair that nothing matters (pessimistic nihilism), or recognize that we humans create our own meaning and strive to enjoy existence on those terms (optimistic nihilism). One way I heard it expressed recently was "The universe doesn't care. But people do."