1 You cant get a toxicroak snorlax or garchomp but u can get thier per evolve forms. You can get coagunk from route 212 and the greatmarsh which is near pastoria city. You can get muchlax by slathering honey on a treee and the coming back some hours later(warning muchlax is very rare) you can get gible from wayward cave. This is a seceret cave under cycling road look it up on the internet for mor info.
2. yes houndoom is a great choice especially since it can take out lucians bronzong( which i REALLY annoying if you cant!
) And the use the dark moves to destroy his other pschics. It will also own arrons bugs types
3 Chancey is a wall pokemon with a lot of Hp.It will serve you well in the ingame but due to its lak of offense i see that training could be hard. it haas a much better use in online though.
4. There r better grass types like roserade.
5 srry im not much of a team rater so i dont think my words would be too helpful
6.u can get the amulet coin in amity square which is a place where u can wwalk with your starter and some other spicific pokemon The coin can be found "Hidden in a hut to the left of the boy with the Drifloon"