Possible

Vegas isn't any better and they taken on 6m more cap, which they use signing a UFA. SAD will never be an NHLer.
Don't think it would be wise to woo and persuade a upcoming college UFA Webber to sign with your team, and then trade him two months later. Future UFAs might be avoid signing with the Leafs in the first place.

I doubt CHI would take Kampf's contract for scraps. If that is what TOR expects, they should probably start poking around to other teams to see if there are any takers.

Marner is gonna get you 100 points and maybe a change of scenery will help him in the playoffs. Holmberg is a cheap decent bottom 6/depth guy. SDA is a pretty decent prospect. Cade Webber is just an add on and a third. In return for their backup goalie, a 4th liner a top pairing d man and they will still have a very solid top 4 d man core.

They get a fifth and a young player to take on 2.4 mil. It’s not like it’s that much money or like they’re planning to be a competitive team in the near future. It’s not gonna hurt them at all. You could change the 5th to a 4th to make it a bit better.

A 4th or 5th doesn't matter, neither have a good shot at even getting an ELC, let alone making it to the NHL, those picks have almost no value in trade. The "young player" you are sending is essentially a career AHLer who also has little to no value. Also, you completely overlooked that there are 3 years left on Kampf's contract and a total of $7.2M in actual salary owed. I wouldn't even do this if it was one year. I doubt any team is giving TOR $2.4M in cap relief for 3 years for essentially nothing, let alone a rebuilding CHI team. If you need cap relief, you pay for it. And if there is some team out there willing to take him for this cheap or even pay for him, more power to ya, but I doubt that team will be CHI.

There is a great TOOL on PuckPedia that is fairly accurate and useful for determining the cost of cap relief and the value of picks. A NJD fan who is a regular on here even took the time to go through trades dating back many years to test it's accuracy, and it was surprisingly very close on almost every single one. A lot of people on here use it.