Is there anything absolute according to your defintion?

I'm not sure how to answer this. What do you mean by "absolute".

In the same sense you used to deny the existence of absolute morality.

In the sense of "deny" as in "refuse to accept the truth of it", I did not deny the existence of absolute morality, I disproved it under a certain meaning of absolute. You have yet to show flaws in my reasoning or to counter with an alternate meaning of absolute where absolute morality is valid.

Your original question "Is there anything absolute according to your defintion?". I need to rephrase this in terms of my definition of absolute; "Is there anything that has meaning in all contexts?". This is to avoid the confounding alternate senses of the word absolute.

The answer is no. This is because I can always find or generate a specific context that does not provide meaning to anything proposed to have meaning in all contexts. For most cases I could simply use electrons as the context. For example, electrons don't have property X, or are not influenced by X. X is meaningless to electrons. For the few cases where this fails I could use algebra. Algebra doesn't contain a meaning for X.

... Morality then only applies to self-reflective level-3 intelligence (cf that comment of mine).

This allows us to get rid of the word absolute and to rephrase the problem as "Can the same morality be applied to all possible cases of level-3 intelligences.".

For the common meaning of morality I think that this simply can't be done. As I've been saying, its all about context.

Eliezer Yudkowsky's Baby Eating Aliens highlights clashing moralities.

But why do you believe that everything happens within the context of physical reality?

Ideally I don't hold beliefs about anything that happens outside of physical reality. If you notice beliefs of that nature point them out and I'll reconsider them. You should feel free to always assume that I don't believe that my claims apply outside the physical universe.

So is there any convincing reason why I should think that the physical reality instead of God is absolute...

I can't answer this question directly for several reasons. I don't know what would convince you. In your current context you may simply be unconvincible. Also, I've actually argued that nothing is absolute for a specific meaning of absolute, so I'm not inclined to now argue that physical reality is absolute.

However, I will try to say something about the belief in God so that I may learn something from your response.

The God hypothesis is indistinguishable from other stories that people have made up and could make up. This leads to the conclusion that God exists in the same way that Sherlock Holmes exists.

For example you might say "God created the universe. The existence of the universe is proof of God." I will respond, "Frud is a tuna sandwich I once made that had a special property, it created the universe, past and future. The existence of the universe is proof of Frud."

Every claim you make about God, I can make about a not-God. I can also state my counter claim in a way that makes it about an innumerable number of not-Gods. Every additional claim that you make about God leaves you with a single God, but allows me to multiply the innumerable not-Gods that collectively satisfy the same conditions.

Every piece of evidence that supports God also supports not-God, but supports vastly more not-Gods than God. For any level of precision the likelihood of God being true rounds to 0, and the likelihood of not-God rounds to 1. This a general problem with non-scientific hypotheses.

So if you wish to believe in God, you will need to do so in the absence of evidence. In your context you might even find practical benefits from such a belief.

A rough answer your original question; you should believe in physical reality over God, because God appears to exist as a story, and physical reality appears to actually exist.