It may feel unlikely that Australopithecus afarensis could scare off large chalicotheres, unless these were quite skittish in nature (something that hardly can be determined with mere fossils).
Dinofelis was actually more adapted to hunt animals on the ground and in the prairies, however, in the show, they are shown hunting early hominids. Although not impossible, there were other felids likely more adapted to hunting hominids and their more forest-dwelling kin, such as pantherines.
The trunk of the Deinotherium is depicted as being rather short, when compared to modern elephants. Although that is suggestive that they had trouble in feeding or drinking, some interpretations favor the short-trunked interpretation, mostly due to the fact that Deinotherium diverged from modern elephants pretty early in proboscidean evolution, so structurally their trunks were possibly rather primitive and more tapir-like rather than elephant-like. The muscle attachment sites on the skull are also coherent with a more developed area around the mouth area, rather than around the nasal area, and that is suggestive of a rather more tapir-like trunk. In this interpretation, the action of eating and drinking would likely be achieved without the strong aid of the trunk, maybe developing a stance like giraffes during drinking or even entering the water sources entirely to drink, as a few animals do, including even modern elephants in the occasion.