bulgie 

Not sure if I have ever lubed mine. A little oil probably won't hurt, but any excess will drip down on the lever and thence to your fingers, which could be a safety concern if it makes your fingers slip off the brake levers. So, just a drop of oil per side maybe, any old oil should do.
No, that tool has the fingers too far apart. I have a VAR screwdriver-style made for TA Pro 5-vis chainring bolts, which are a couple mm smaller, works for Suntour Barcon nuts.



But really, most any wide-blade screwdriver can work. If the shaft of the bolt intrudes, preventing the screwdriver from staying seated in the slot, you can make a custom tool by filing or grinding a slight recess in the center of the blade, leaving just enough unmolested on either side of the recess.

You can also replace the Suntour nut with a generic nut from the hardware store. I think they're M4 x 0.7, a common size — someone correct me if I'm mis-remembering. Don't bother getting nyloc nuts, the bolt isn't long enough to reach the nyloc material. I think the standard nuts take a 7 mm wrench, not a screwdriver, and they won't look "right", but they'll work, probably more reliably than the original.

Someone, I forget whether they're on BF, designed a plastic part for 3d printing, that lets you replace also the inner nut, the one that nestles into the hexagonal recess. Then you do use a nyloc nut since there's only one nut, no jam-nut. He put the file on some downloadable forum like Thingiverse, so you can make your own if you have access to a 3d printer. Maybe someone here will remember who or where. This was a number of years ago and I never heard of anyone having any problem with that system, so I think it's proven reliable. Or maybe the people who hated it just kept quiet? Seems unlikely...