The Christian God is NOT simple.

[Anomalocaris]

I wholeheartedly agree that some traits are quantifiable because they are based on fixed definitions outside of perception
Mass for instance (as in your example) is universally defined as "how much spacetime an object displaces".
It can be measured in different ways but the same value will be reached completely independant of what is perceived.
When you use a term like "heavy", "light", "soft", "bright", or "complex" those are JUDGEMENTS about an entity and
they depend very much on the perceiver. A child may say a carton of milk is "heavy" but an adult may say it is "light"
Independant of those judgements, the carton has the same mass.

You confuse qualitative judgement with quantitative attribute. The underlying quantitative attribute of the thing remains exactly what it is no matter what qualitative judgement your fickle mind pass on it. 3 grames is heavier than 2 grames regardless of whether you think 3 grames is heavy or light. If god is infinitely complex in the information sense than it must require more data to describe than anything with a finite information content, regardless of where you place the line between your notion of simplicity and complicity.

All I get from your statement, is that in order for "complex" to be quantifiable, there has to be a fixed definition of
"complex" that is agreed upon. If we agree arbitrarily that "complex" is an object that has more than ten sides
then a ten-sided object is "simple" and an eleven-sided object is "complex". Someone outside of the agreement may
choose a completely different definition and so on. In order for something to be quantifiable, it has to correlate to
a fundamental principle that is true regardless of the perceiver. Mass, luminosity, composition, etc. those are
qualities that cannot vary between perception. complexity, attractiveness, sharpness, etc, are qualities
that depend on the perception of the observer and thus cannot be quantifiable.

So? a 10 sided object still has 1 more side than a 9 sided object. If you imagine a object with infinite number of sides then it would still have more sides than any object with finite sides. Doesn't matter whether you call that "sidedness" or "complexity" or "divine polygonity".

Because the term "complex" isn't defined, you can't say X is more complex than Y
and you are implying that "simple" entities cannot create entities with more "complexity" and if that were the case then life would not be possible.
A single cell (with an arbitrary complexity value of X) , can become an entire organism (with an arbirary complexity of X + Y). Whatever the measure
of complexity, the second entity carries with it many more times the original entity and thus could be said to be "more complex"
We can predict very "complex" things (like evolution) with very "simple" rules (like natural selection) (the quotes are because the terms
are relativeistic)

Incorrect. A simple entity can only create a complex organism by taking complexity from somewhere else and adding it to what would become the complex organism. It can not manufacture complexity out of thin air. So to fully describe the simple entity, one must also descibe the complexity it would use to create the complex organism. Thus an appearently simple entity would be seen as simpler than its product no longer if one were to descibe all involved in the process of making its product. Modern physics say information can never be created or destroyed. There are only complexity about a single entity that created an appearently more complex organism that you neglected to describe. There are no complexity that the simple entity actually create.