Ignoring everything else, that is a very odd thing to say. Nothing can be valuable when you have an infinite supply of it. If you had an infinite number of days, then every day would be worthless. It is precisely the knowledge that your days are limited that makes each and every one precious, the need to make the most out of every moment, because soon they will be gone and you'll never get them back. What difference would today make to an immortal, or tomorrow, or next week, or a hundred years from now? It is the fleetingness of life that makes it meaningful. 
While that's certainly the case in economics, with most goods and services, the philosophical is a different matter entirely. Each new day will have new things, and extends life, which makes each new day valuable. Having no more days marks the end of life and every memory of days prior. Effectively erasing them for the one who perceived them. I think the main concept of this discussion is oblivion. It reduces life to a zero sum game. Pointless. You are arguing from the standpoint of being alive. Oblivion takes away all value. So yes, eternal life is what gives these fleeting days any value at all.
-He beated them,the way in which he did that is irrelevant it is just a matter of technicalities here ,i consider that as a victory for the dread wolf who managed to lock them all for thousands of years yet the ancient elves were unable to live in comfort without the fade.
-He did not create the Inquisition he merely offered the castle. the Inquisition was founded by the right and left hand of the Divine.
Solas was weak and very much killable during the events of DAI so he was clever enough to use the organization as a means of defense for himself,that he did not recovered the Orb is not what it matters,since his life as elven god is far more important than one of his artifacts.
-The eluvians were in the hands of Briala then passed to Solas,Flemeth is irrelevant here.
-I know from codex and the library of virrdathara of what they were capable of.
-Elgarnan used Titants to build his own statues
-Ghilanain created new animals species like the Cetus tremendous marine monsters and many others ,her knowledge was great
-Mythal was able to kill TItans
-Andruil was able to enter into the abyss
-Solas is able to petrify at wish and possess great knowledge
-Falondin rules over the deaths
ecc...
-Keep believing it against mere mortals,he fear them so much that he openly reveal who he is and even saved the Inquisitor.
The world is akin to change that's inevitable
What's good is supposed to be in knowing that days are limited?
Eternal youth is a gift more than desirable as every aspects of a being can be better developed by it,thousands of years to study or thousands of years to train ecc
Beings who possess such gift are inherently superior and when they are tired or stressed in DA they go to sleep to wake up after centuries and always be testimony of the change of the world,eventually they will die as well but only at the end of the world or if they are killed.
Cole describes it as the wolf chews its own leg off to escape the trap. Not exactly a victory. And for all we know the evanuris are safe and sound wherever they are, patiently waiting for the Veil to drop, and when it does they will emerge just as powerful as ever. You like to post about immortal beings? Well, what Solas did is nothing more to the evanuris than the casting of Ice Wall in a narrow corridor. When it runs out... look out, because here they come.
He simply didn't get caught, and that's mainly because there was no evidence of his involvement in the events of the conclave. Not the same as him tricking the Inquisition though. You can go through the whole game being suspicious of Solas and not believing anything he says, but there is no evidence for you to act against him.
According to Solas, his agent failed to get the passphrase from Briala, and so he had to "override the magic personally", which was actually Flemeth's doing, and she willingly gave this to Solas. Then after Solas had it, the Viddasala found a way to activate the eluvians and moved her agents in to take the various elvhen locations. Solas needed the Inquisition to get rid of them all.
You have legends. There is no proof that they are correct. All those things could have happened in the Fade, meaning, imagination. I don't remember anything about Elgar'nan using titans to build anything. There is a codex stating that many of his servants cut away at a mountain for 1,000 days or something like that to make a statue in his honor, but that's it.
Ghilin'nan may have created creatures, but it's likely this power came from the Fade and used spiritual energy. It's also possible that these creatures only existed in the Fade, thus reducing them to mere imaginings.
Mythal slayed one titan that we know of, which shouldn't be that difficult. The Inquisitor can destroy one of the titan's guardians, and theoretically if he had just kept on doing this at various points inside the titan, then he could have slayed a titan as well even without the benefits of Fade energy to enhance his powers as Mythal would have had.
Andruil needed to craft armor that would allow her to go there, and even after that she still went mad trying. Mythal had to put her back in line.
Solas can petrify non-mage Qunari at will. We don't know if his ability works on other races or on other mages. So what if he has great knowledge? He hasn't made good use of it so far.
Falon'Din is said to be able to walk in the Fade physically. We don't know what significance that has yet.