I see,
1) The fields are created by force of will, meaning they do not require any condition to be met other than be strong of mind.
- However, if the fields are large and need to be 'upheld', the force of will needed increases and so does the concentration needed. The user needs to give the power his full attention and is unable to do any other tasks until the field fades.
2) The range is within the user's proximity, there isn't a preset range for this power other than it has to be 'not too far away' to be able to sustain it.
- If an absolute range is required, then I'd say about 15-20 feet in any direction.
3) The size of the fields can differ as said before, ranging from just coating his blades to the user standing near the railing of a ship and maintaining a temporary field that covers the entire side of the ship and has a thickness of 5-8 feet.
I hope this all makes sense ... ^^