1) Pin 9 is the grid of the EF86, that's where the input goes - oh, and since I didn't see the input resistors on the layout I'm assuming you plan to hang them on the jack (?)
2) 1n4007 ought to work
3) I would use 1/2 watt, except as noted on schematic
4) If you only have two wires on the heater secondary (i.e., no center tap) then you probably have 6.3VAC across the two, which is what you want. You can (carefully) measure the secondaries to confirm AC voltages if you are unsure of the exact transformer specs. But first, use your continuity tester to suss out which leads or lugs are part of the same winding.