Supplying more current to a current limited DC motor
Your question is very difficult to follow without a schematic. If this answer does not answer the questions then please use the schematic editor to add a schematic to your question.


Yes. The most wear and tear on contacts is caused by arcing at contact closure and contact opening. Parallel relays or contacts will never open or close at exactly the same time. The first to make and the last to break take all the pain.
There is no problem paralleling relay coils - just the contacts.
I don't understand this question without a schematic but I suspect that you are asking can you use the relay contacts to short out the motor for rapid braking. If you do this you are effectively short-circuiting a generator and the current spike could be relatively huge. You should probably switch in a high powered braking resistor to limit the braking current to a safe value.
Schematic required.