1. The amount of colored ore you get is a set percentage chance for the location being dug at (despite dev's claims otherwise), that varies by location, but stays the same even when the ore changes type (only applying to an Iron site when it gets elevated to DC or SI by tools). supposedly the elf bonuses apply to it, or (if wood is any indication) to the amount of digs you get.
2. For DIGGING ore, all the gloves apply for is to determine the TYPES you mine, and if you will succeed in the dig. At 99 skill (real or modified) you can dig all metal types. At 100 skill, you can dig stone and sand, if you've read the books, and will no longer have the chance of "failing" a swing of the tool (bringing up no ore).
3. The chance to SMELT colored ore is 50% at the skill level where you first can mine it, progressing 0.2% per 0.1 skill gained. So, any skill amount that raises you is better for smelting.
4. When Smiths RECYCLE/SALVAGE smith-type items, the ingots returned is 0.66% times the MINING skill, rounding down. Most items give their highest metal return at 101.1 or higher skill (101.0 is JUST under 2/3, so the leather gloves won't cut it). So having that extra bonus is especially when recycling/ You also get an extra ingot back per item when using a Salvage Bag to recycle smith items.
5. And, yes, you can enhance them. I look forward to the possibility of imbuing them as well.