no, you shouldn't go above 20 unless you're sure the item needs it, as in draws over 15 amps -
no, 7.5's won't necessarily burn out, try them and see -
an 1156 bulb is common for 12V parking lights, not "big" and I believe the Guide 31 was used for parking lights in some years, 7.5 might do, 15 at the most
you could use a meter to find out how much current any item item draws, your phone charger should say right on it
Bill
