I think going on about truth as applied to theories is a bit over worked.
Most of the time we are using the word colloquially. That is, truth is what we are "sure enough" is correct. And in that way many scientific theories are treated as "truth". All the discussion about being tentitive is true at the leading edge or for something like general relavity where there are still some concerns but for the germ theory or atomic theory we have arrived at something that is treated in a practical way as true.
The same applies to the ToE.
The problem is in these discussions we get various
different meanings or connotations of the word "truth" tangled up.
Mathematical "proof" in one thing and is absolute "truth" within in confines of the particular mathematics.
Religious "truth" is something else and not the same as the practical, maybe temporary "truth" we arrive at with science.
Scientific "truth" in NOT the same as the above but most of the time it is taken as firmly true for all practical purposes. I think it is important to remind all of us of the tentitiveness but not to confuse that with very, very firm assuredness.
So, after we have put the philosophy of science down as the context, that something is "proven" and "true". Just that it is only as those words might be modified and defined within the context established.
That context does not apply elsewhere as in math or religion.