That is correct, the maximum temperature of the heated bed is 240C, there are software and electrical limits in place to prevent it from overheating. Exceeding the temperature of the heater will greatly diminish its lifetime. Furthermore, practically speaking there will be a 10-15 degree discrepancy between the temperature of the heater and the surface of the board, so the maximum temperature the board will see is around 225C.
If you wish to apply solder paste manually and reflow with the V-One, you would have to use a lower temperature solder alloy (we use Tin Bismuth) or use a hot-air gun to push the temperature over the edge.
It is certainly possible to manually dispense by turning the gear by hand - but yes - breaking the nozzle is a possibility if you are not careful. If you do end up trying it, I recommend applying a little bit of pressure and exercise patience by letting the solder flow out by itself, forcing it out might result in a pierced plunger, which would wreck the cartridge.