I had a Cimarron-imported Uberti convertible .45 C/ACP a few years back, and it was a nice revolver (with a pretty finish).
It was perfectly durable with even mid-level loadings. But it's a SAA . . . it's not a particularly strong platform for hotrodding the .45 Colt.
To answer your second Q, I'd say no. In fact, I'd say that the .44 Spl's tiny bit of decreased diameter gives you notably more security in your warming up your handloads in this sort of gun (not that you're going to do so, or that you should).
FWIW, I happily handload .45 Colt, .45 Cowboy, .45 AR and .45 ACP, and I shoot them all from revolvers. I have no interest in changing over to the .429 bores, but if I'd started out down the .44 Spl/Mag path instead, I'd see no reason to start with the .45s.
And, FWIW, the .45 single-action I carry on
my hikes - not really fatter than a SAA - is the New Vaquero.