"It is only through the quality, the power and purity of the Dharma itself that something can change in us"
i.e The Dharma as an 'itself' implies external teachings.
Here you are clearly confusing the moon, with the finger pointing at the moon. Language can never clearly express/explain experience. Also, let us not forget language barriers. Lama Gendeun Rinpoche was a Tibetan refugee who escaped to India and was then sent to Europe (in 1975) by the 16th Karmapa to teach Dharma. He spent thirty years in solitary cave retreats in Tibet and his teachings are based on his experiences.
There may be no atman, but there is always cetana.
And there is somebody there that has volition? Where exactly? Can volition exist without a self? How exactly?
Does it not take a very great deal of effort to cultivate bodhicitta?
Nope, all you need to do is cut off ego-clinging and you'll find bodhicitta was there all along. Ain't the Tathagatagarbha great!? Take an Arhat, for example (no please take one, free of charge, no strings attached): "An arahant is a person who has destroyed greed, hatred, and delusion - the unwholesome roots which underlie all fetters - who upon decease will not be reborn in any world, having wholly cut off all fetters that bind a person to the samsara." So, are we under the delusion that, upon achieving Nirvana, bodhicitta would not spontaneously arise for an Arahant? That by destroying greed. hatred and delusion one would not (automatically) be filled by an overwhelming sense of (enlightened) love and compassion?
Whether one goes clockwise direction (develop compassion, love and wisdom) or an anti-clockwise direction (destroy greed, hatred and delusion) they always come back to the same point.
PS I'm sorry I didn't know the stanza was old, next time I'll whip you up fresh one and I'll throw in the choclate sprinkles "on the house".