Glaceon is a beautiful pokemon, but as you said, it's not that great in competitive so you really need to build around it. There's a lot of things to consider, I'll just go through each pokemon. Sorry don't want to come across as insulting the whole team, I like the pokemon, it just needs some fine tuning.

Kilowattrel: No idea why you're running heavy-duty boots, there are rarely hazards in VGC to make it worth it, and stealth rocks would only do 25%, and spikes would do nothing. You're also running weather ball when you have 3 other pokemon running ice type moves, steel is just going to wall you. I wouldn't rely on Kilowattrel as a sweeper. He can hit pretty hard, but is extremely frail. I'm also not sure who's benefitting from tailwind besides itself and glaceon. the others want trick room.

Glaceon: If this is going to be your main sweeper you need more than just ice type moves. Shadow ball would help, or even Terablast ground to hit the fire and steel types that resist ice. It does need a lot of support, aurora veil helps, but if needs both aurora veil and tailwind, it's going to be riskier setting up.

Abomasnow: Honestly pretty good build. I would normally say blizzard since he's the one setting it, and the most likely to hit with it, but I understand having him physical as he's your only physical attacker. His attack is 92 which is ok, but if you run into a special wall you're really going to struggle getting through.

Slowking: If you're going to run trick room slowking, oblivious is a much better option to make you immune to taunt, and covert cloak means he can't get flinched, so it's a much more reliable trick room setup. You already have 2 other ice types, you need move diversity. Give him a stab water move. Yawns do force switches, but I don't think you have enough offensive power to capitalize on punishing those switches

Sableye: You can't/shouldn't run trick scarf and fake out. Either you trick turn one, and then can't use fake out, or use fake out and lock yourself into struggling. He also has a lot of other tools you probably need more, like will-o-wisp, or ally switch

Not really sure what Gastrodon brings to the team. He's a great counter to Dondozo, but that's about it. Not many water types to worry about in this early meta, and might want to switch him for something with more power