Hey seb125, nice scarfmence team you have here. It's pretty well balanced but hopefully I'll be able to help you out with some ev spreads/ movesets and some team member decisions.
First I'll start with recommending forretress over skarmory although forretress can be dead weight at times salamence really appreciates a spinner on his side and forretress is about as good as you're gonna get. Also, to make forretress more of a presence, I would recommend gyro ball over spikes so it can do some extra damage to things locked into outrage, or sweepers such as scarf terrakion. You would be putting out more damage than spikes and it isn't something that can be taken off the field so it is definitely more reliable. To maximize damage output use a relaxed nature with 0 speed iv's.
Next, I would keep conkeldurr over rotom-w. Gliscor would only become more of a problem with 3 scarfers and conkeldurr can take out some opposing dragons, steel types, and walls such as Gliscor and landorus-t.
My last suggestion is pretty minor but will help a ton. I would run taunt over ice beam on jellicent as it allows you to take on opposing stall much better. Also, I would take 84 Ev's out of your special defense and put it into speed. This allows jellicent to outspeed base 70's with no speed investment such as politoed and skarmory that could otherwise cripple jellicent with toxic or set up hazards. Ice beam may seem great but you now have ferrothorn's gyro ball and conk's ice punch to deal damage to those dragon types. Plus things like Dragonite can't set up as easily as before.
Hope I helped and good luck with the team!