The first point is very valid and we don't know if we can truely trust the gods to keep promises.
Especially with Hermes being the god of thiefs as well so there might be some trickery invoved.
But I don't think that Argos or better Nikos are any threat.
Because even in the Story Asterion himself said that the Argos always leave after a certain time and they usually just play mind-tricks with the current master so they punish him more harshly or send him to the valley where he is hurt by the monsters.
Nikos also said that he is just playing a role and he doesn't agree with the punishment of Asterion so I think that he was genuinely glad that we were different from the masters in the past.
He and Asterion also had a very friendly interaction and they talked about if they would have been friends if they met under different circumstances.
Sure he is a snake and that might not leave the best impression and there might be a stigma coming with his species but then again he never really tried any funny business and held up his promises.
Also with the insight that we can apparently gather during the ruthless route I dont think that he double crosses us behind our backs.