Do these sorts of value depend on the valuable thing existing?
I'm asking just because I'm suspicious of valuable things which do not always exist, and want to (eventually) find the terminology for the opposite.
First, there is but one absolute value:
These [i.e., persons, defined as ends in themselves] are not merely subjective ends whose existence as effect of our action has a worth for us; but rather objective ends, i.e., things whose existence in itself is an end, and specifically an end such that no other end can be set in place of it, to which it should do service merely as means, because without this nothing at all of absolute worth would be encountered anywhere; but if all worth were conditioned, hence contingent, then for reason no supreme practical principle could anywhere be encountered. (Groundwork for the Metaphysics of Morals, Ak. 4:428, Cambridge p. 48, bolded by me)
He clearly states that without 'things whose existence in itself is an end' there would be 'nothing at all of absolute worth'. The carriers of this absolute worth are rational beings, as clarified once more later on:
Rational nature exists as end in itself. The human being necessarily represents his own existence in this way;... (Groundwork for the Metaphysics of Morals, Ak. 4:429, Cambridge p. 48)
Now one aspect of your question, as I understand it, is how this worth is bound to the existence of the rational being at hand, i.e. what happens if the rational being seizes to exist in a relevant sense (i.e. death) and if this does in fact change something.
I will have to admit: I only have a partial answer on that one.
Here, we have to leave the Groundwork and have a look into the Critique of Practical Reason, the fundamental book on Kant's practical philosophy. In the Dialectics, Kant goes into some detail how the existence of (finite) rational beings has to be thought.
I'm not happy with the translation, but it is the only one I have at hand by now. I will therefore quote the key part and paraphrase other parts of the argument afterwards:
The full commensurability of the will to the moral law, however, is holiness, a perfection, of which no rational being of the sense world is capable in any time point of his existence. But since it is nonetheless required as necessarily practical, it can be encountered only in a progression going infinitely to that full commensurability. And it is necessary, according to principles of pure practical reason, to assume such a practical advancement as the real object of our will. But this infinite progression is possible only under the presupposition of an existence and personality of the same rational being, continuing into infinitely (which one terms the ‘immortality of the soul’). (Critique of Practical Reason, Ak. 5:122, Translated by Philip McPherson Rudisill Posted September 18, 2012, bolded by me)
But this is only a 'postulate', i.e. a 'theoretical sentence', and does not in the least say anything about the theoretical reality of this immortality. But as we, in acting morally, have to presuppose this postulate and act accordingly (according to Kant), it gains practical reality.
Within Kant's own framework, the rational being does not seize to exist with death if it comes to practical concerns. This does not mean that it 'really' continues to exist (we cannot know for sure), but that we have to act as if it were (we have to presuppose it).
The absolute worth and dignity of rational beings, which is bound to their existence as end-setting beings, does therefore not seize either. Because dignity/absolute worth is a practical category, i.e. when talking about value we already are talking about what I called 'practical concerns'. Dignity is therefore absolute (i.e. not to be relativised) as well as infinite (i.e. in time). It has nothing to do with things-in-themselves, though.
Well, this is valid at least for the critical Kant. There are some not very well researched shifts within his Opum postumum that arguably would make another answer possible, but I am not (yet) deep enough into it to build an answer on this.
Value is the word here with 'fuzzy logic' behind it's definition.
The Absolute, i.e. absolute Truth, exists, regardless of whatever BS you, or I, or another entity or individual thinks, says, writes, rules, and/or does, to infer differently.
To seek absolute truth regarding an issue arrayed before you for analysis and review, is the only way to fully comprehend Kant's 'categorical imperative'.
In summary, absolute truth exists, an individual must seek their absolute truth, and when that is accomplished, all of the absolute truth, i.e. the Whole Truth, becomes accessible to that individual.
Whether the individual accesses and understands the Truth arrayed before them is entirely up to the individual's free will ability to choose to utilize the 'genius, and more', capabilities of the intelligence they received at the moment of their creation.