1st part: The effect of the Ability applies to TMs. Notice the distinction between "the attacks it uses" on Okidogi and "an attack it has" on Dipplin from the same English AND Japanese set.1rst part, I believe it does work like that, but I'm not sure 100%.
2nd part, yes, you will be able to attack for only 2 energies. the special provides both the fighting and darkness requirement at the same time. but only give one energy slot at a time.
If it makes any sense xD