I think you're getting yourself worked up for nothing over the dropout spacing, a few mm either way doesn't really make any difference. Also the wheels, it is not a problem to find a builder who will make you a decent pair of wheels with single speed hubs and clincher wheels, if that is what you want.
Get yourself a decent frame first, one that you like with either track or horizontal road dropouts and worry about everything else later.
I think you're getting yourself worked up for nothing over the dropout spacing, a few mm either way doesn't really make any difference. Also the wheels, it is not a problem to find a builder who will make you a decent pair of wheels with single speed hubs and clincher wheels, if that is what you want.
Get yourself a decent frame first, one that you like with either track or horizontal road dropouts and worry about everything else later.