You are the same height and inseam as myself. I typically ride a 55/56 and like a 56cm tt.

I run my saddles on all of my bikes, with some minor variation due to shoes, peddles etc, at about 75.5 cm.

Sound like you bike fits you to me and just needs some fine tuning. A 58 would have been too large. If you have your saddle higher than 76cm from c/BB to crown of saddle, you are getting it out of range, people tend to run their saddles too high these days because ti looks cool, 75.5ish is about right for your stated measurements.