Welcome from just north of the border.

1. 16oz. Mine have proven superb in the winter wet around here and although I haven't tested them in the summer heat (if you can even really call it that here) I see many gents at the summer games looking perfectly comfortable in them. 13oz probably wouldn't be bad if you decide to go that way though.
2. dunno, but yeah, you get what you pay for and you really should try and get the best you can afford.
3. Probably only how it feels to your hand ... and other parts.
4. A traditional kilt wants to sit with the buckles at your natural waist with 2' rise above that for construction purposes. I would not recommend trying to 'better' the design.