Rache

Sabrina is actually stronger than Koga, but that's the right sort of solution. Either Lt. Surge or Erika must have been skipped.

Route 120 should be quite good for you then - all hordes when surfing are 5x Marill.

Not all 3-mon hordes were bumped up to 5 - very few were, and only due to the species being frequently hunted (and the mainland of Hoenn being given more in general). If you're looking for a good HP EV training location in Hoenn, try surfing on Route 120 - it was adjusted to give a reliable 10 EVs per battle. The change to Sweet Scent only affects routes that had hordes of both 3 and 5.

These moves actually did exist in Black and White, despite the lack of Kyurem forms. They can be called via Metronome.

We don't ban players who haven't broken any rules. Additionally, please do not publicly call out players. As others have stated, you can block users and/or auto-decline battles. Duel requests are separate from matchmaking too.

Shadow Ball is a special move - it's not good on Snorlax, which is a physical attacker. X items are single-use, yes.

It should already have Body Slam, which is arguably its best move. It will learn Crunch on lv49, which is a good option to hit ghost types with. If you haven't used your Brick Break TM yet or are willing to buy another, Snorlax can make good use of it to hit rock and steel types. Earthquake would do the same thing (but better), but you won't get it until you have 8 badges unless you buy it from a mart. Your 4th move could be just about anything - a status-inflicting move or HM perhaps, possibly Rest if you don't like using healing items, maybe a stronger normal type move like Double-Edge for when Body Slam isn't hitting hard enough. Snorlax has a lot of good options here, so go with whatever suits you best. The thing to keep in mind when using Snorlax is that he's very slow, but also very bulky. He won't attack first often, but he should be able to take most hits well, especially from special attackers. It's a very strong Pokemon, and should be very reliable for a lot of the gym, Elite Four, and rival battles.

Your team is well balanced. The only type you don't have a defensive answer to at the moment is psychic (2 weak, 0 resist). Snorlax has very good special defense, so while it won't actually resist the type, it should be able to handle them. Alternatively, a dark or steel type would patch that weakness up very well, but the options for those in Kanto are a bit limited without using the GTL.

Using a full team of not-fully-evolved Pokemon (and one of the early-game bugs) is likely a big part of why you're struggling so much here - you don't have the stats to win, and this is one of the more difficult gyms due to her type variety. Gardevoir tends to perform very well at this gym, but since you got your Kirlia to the level cap without evolving it, it's stuck as one until you win (unless you make it a Gallade, which won't be very helpful here). Your best bet may be to switch something that isn't helping you much at the moment for an ice type that can also take a hit, like a Dewgong, Piloswine, Cloyster, Glaceon, or Sealeo.The GTL should have plenty of each.

The "Switch" battle style was intentionally left out as it undermines the AI and makes the game too easy. All battles are instead done in the "Set" style, which was also an option in the handhelds.

You started the game with the national dex.

I'd argue that the music change makes it much, much better.