1) There are systems designed for oil or grease, but normally not both. I use oil on 2 of my machines because they came equipped with automatic oilers. The other machine (Haas TM-2p) gets grease, manually, because that is what the manufacturer recommends. In the case of the Haas, the lines are brought out to the front of the table for easy access. I think the recommended lube frequency on the Haas is once per week, or 40 hours.
2) I would just wire a relay through the E-stop system so the lubricator comes on when the E-stop is pulled out.
3) Bijur Delimon Automatic Lubrication Systems : Overview