The core point is that without an exhaustive proof, there is no doubt that no scientific theory can be guaranteed to hold true in any possible case. Galilean relativity, Newton's law of gravitation and classical mechanics are golden examples. They were thought to be always true, "unbeatable" so to speak, and they were consistent with centuries of experiments. There was no evidence that they might produce quite inaccurate predictions. We all know how it went: they fail miserably under some circumstances.
Not at all. They produce perfectly accurate results that are suitable for the environment in which they were conceived.
😦? They were thought to be universal and they are not.
You seem to be wanting to introduce a fallacy ... that of assuming that there are mysterious circumstances that alter the characteristics of chess [ . . . ] The rules do not allow for weird, relativistic effects within chess, so you're wrong again.
Is this a straw man? 
What I and others are saying is that there might be yet unknown lines which could disprove the assumption that chess is a draw. While we could safely ignore that Newton's law of gravitation is very incorrect under some circumstances and happily live with that (GPS satellites would not work properly, but...), for a solution a single unexpected line can make all the difference.
In game theory, "optimal" is not a casual attribute. For chess, it means that an optimal player would be unbeatable in a match with an even number of games: if the game value is a draw, the optimal player would at least draw every game; if it's a win for either colour, the optimal player would always force the win with that colour. Therefore, the optimal player cannot score less than 50% of the points. Without a mathematical, exhaustive proof, a player cannot be guaranteed to be optimal, exactly like a scientific theory, without an exhaustive proof, cannot be guaranteed to always hold true.
This is confused. The first part is unnecessary. At least we know what we mean by "best play" or perhaps, "optimal", because we've been talking about it, in various threads, for about four years now and we did reach a consensus. Off the top of my head, optimal play is that which doesn't alter the game result negatively, for the player who made that move. Some like to say "from the game-theoretic value" but that's unnecessary, because it doesn't add anything useful. Just an illusion of grandeur.
What about the second part?
This is not what people expect, when they read something like "the game xyz has been solved". They think about a definitive solution, that nobody will be able to disprove, ever.
You could never be sure that there wasn't a mistake in the analysis, due to a glitch of some unexpected kind. So wrong again, I'm afraid.
That is a point already made by @MARattigan. In fact, I said that people do expect a definitive solution, not that they can be 100% sure that a computer-assisted proof is correct. But the point is: is a statement like "chess is a draw because... [unproven motivations]" as acceptable and reliable as a statement like "a computer-assisted proof by exhaustion established that chess is a [draw, win]"?
I went to Yugoslavia a number of times, always hitch-hiking. The only objection was that it was illegal to be asleep in a public place. That included sleeping out at night. I became adept at choosing half-built houses and they were always clean and gave protection from rain. I liked Dubrovnic very much and often went. Had a friend there. Climbed a bit in the Albanian Alps and travelled with some Austrian hippies who were exploring religious centres of the old Serbia, right up near the Albanian border, formed before Serbia contracted. I loved Yugoslavia and of course it was one country, very diverse. Never got to the Novi Sad area but that's more or less the only bit I didn't see. Liked the Macedonian people and those up North, around Maribor and Zagreb. In fact, everywhere.
In Bulgaria while hitch-hiking somewhere near Plovdiv, was very tired indeed and found a big field with a lot of small clusters of undergrowth. Walked right to the middle of it to get away from people and hid near a small copse and slept for the night. In the morning was woken by some noises. Noticed some Russian soldiers about 300 yards (metres) away. Got my stuff all together, packed up as fast and quietly as I could and started to walk back to the road. A sleepy looking Russian came out of a bit of undergrowth and we were face to face, so we sort of ignored each other and carried on. Then some of the bits of undergrowth started to move, shedding bits of tree behind them. Making a clanking sound, these trees were.
I had spent the night right in the middle of a Russian tank battalion and all the clumps of undergrowth were very well disguised Russian tanks .... about 20 of them. 1969.