1) I wouldn't recommend using the cheapest method possible, but that's just me.
2)The data sheet says 2-6amps. This board appears to use the same chips as a Xylotex, and Xylotex says you shouldn't ever need more than 5amps for their drives. So 6 amps should be good, but more won't hurt you. It probably won't help either, just saying that if you have a 10 amp supply, it'll work fine as well.
3) from the manual you linked to:
The TPX, TPY, TPZ, and TPA are clearly labeled on the first page of the manual, as is the VBB common. Black lead to the VBB common (ground), and red to the TPZ, TPY, TPZ and TPA.Current adjustment is made with the aid of voltometer at test points (TP X, TP Y, TP Z, and TP
A). Be sure to make contact with COM probe at COM connection point at VBB INput.