The Pinarello Gran Turismo was designed for 700C wheels. The OEM brakset was Campagnolo Gran Sport long reach which would give about 5mm more pad adjustment and accommodate the 4mm smaller BSD of 700C. Typically, bicycle intended for use with fenders use longer reach brakes.
You can get more tire clearance from the stay bridge by dialing back the dropout adjusters, as they are set for maximum forward wheel position. This will give more chain wrap and a longer gap, which will slow down the shifting a bit and may require slightly more overshift, but shouldn't be a big issue unless the shifting is indexed.
If the spoke tension on the front feels low, it almost certainly is low. the deviation from normal has to be fairly large to be detected by hand.