Ji,
If I rember correctly the "lug" on the powervalve linkage isn't used for valve alignment.
When removing the linkage you rotate the retaining nut until the hole and lug line up, then insert a dowel (small screwdriver will do), you then can apply pressure to the nut to remove.
Damage to the powervalve can result if this is not carried out.
Best of luck, I have a test on one of those I think, if you want a read.