Interesting little detective hunt!
For the first passage, the Sanskrit is at Avs 38.
The background narrative is a Jataka story, which explains why the “blessed one” is seeking after good speech: in fact it is the Bodhisattva, then born as the son of King Brahmadatta in Benares. interestingly enough, his desire is said to be a dohada, which is normally the pregnancy cravings. The idea of transforming his body is not clear to me, I would have to check the sanskrit more closely. But it seems as if there is a confusion stemming from the shift in the meaning of the word yaksa. In the early texts, it simply meant “spirit”, and is neutral, applying to both good and bad beings; Sakka himself is identified as a yaksa. Only later did it come to specifically mean malevolent ogre. So I suspect there has been a later explaining away of this detail.
The Dhamma verse here has a number of parallels; the Pali is at Dhp 169. A related verse is in Ja 384. The parallels for all these texts list various other contexts. It’d be worth checking the commentary for both the Jataka and the Dhammapada. However I do not believe the prose story has a direct parallel in the Pali canon.
For the second one featuring Devadatta, the Pali source is in the source you supply. It is the Sanghabhedakkhandhaka, and you can find the passage translated at Kd 17. Each Vinaya has its own version of these events.
The third one is hard to trace without more context, but from what I can glean it refers to a prophecy of Ashoka. Ashoka is nowhere mentioned in any EBT, so if there is a Pali parallel (which I would hazard is unlikely) it would be in some later text.
I cannot identify the story of the deva who had formerly been a sea monster. It says “untraced”, and it may be a lost tale.
The story of the sweeper seems, according to the Dictionary of Pali Proper Names, to be found in the commentary to the Samyutta Nikaya, the Sāratthappakāsinī, vol 2, p 217 of the PTS edition. However I don’t have that edition, and I cannot locate the passage.