Higher volts will cause a previously OK fuse to go pop, you are by spinning the prop faster causing the motor to draw more current. If you want to use a higher voltage then you need a smaller prop to give the same amp draw, power will still be higher
Sounds like you have too many fuses, you only need 1 fuse, in the positive wire from the battery to the ESC, all the others are creating resistance and inefficiency. Make all the wires as short as possible and as thick as possible, minimum 12 AWG better is 10 AWG.
Is the motor water-cooled, at 25 amps I would consider brush tab cooling as well as can cooling, involves soldering on 2
separate pieces of copper or brass tube to the wire connections of the motor and connecting them with silicone hose to the cooling circuit.
there will be no difference between the 30C and 25C batteries, C only gives the maximum amps a battery can output.
Nick