Blues

none of those trades go through. columbus wants nothing to do with jake allen, nor do they want to trade away a good cheap defenseman signed for 3 years. tatar is worth more than what you are sending out. sanford isnt worth a 3rd

I disagree with all of your points.

Columbus needs a legit 2C, has no passable starting goalie, and has a wealth of defensemen to deal from. Not saying Allen is a legit starting goaltender, but he's played the role well before and could benefit from a change of scenery, like Dubnyk. We could retain like a mil or something if that's the hangup, but I don't think that's an issue for them right now.

Montreal is weak on the left side and has a lot of young forwards coming into the mix. I don't think Tatar is someone they would look to re-sign (maybe I'm wrong?). I think they would be looking for a package similar to this. Could offer Blais instead of Fabbri, but I think Fabbri will easily prove himself more valuable this year. This is probably more of a mid-season deal.

In a world where Zac Rinaldo has gone for a 3rd round pick, I think you're nitpicking here. Sanford is young and has had strong flashes this year when not injured. He played well early in the season and complemented ROR's line well in the playoffs as well. Florida has some forward depth to fill.

Columbus is in a rebuild now with no picks. so the 3rd coming back would help but is essentially just to take jake allen who sucks, dont spin it any other way, that defense for the blues was pretty damn good all year and when he was at the helm they were the worst team in the nhl. you are essentially trying to dump his cap and get a capable backup (korpisalo is only 25 and will be the starting for the blue jackets). Jenner is 26 why cant he take a shot at being their second line center? or they could resurrect brassard career and sign him to a cheap 1 year deal. OR just wait until schenn hits FA and try and sign him then. Columbus isnt contending this year. their entire offense was just gutted, trading one of their captains, a good young dman on a great contract and a young unproven goalie for what might be 1 year of schenn and a crappy jake allen. WOOF.
Moving on to Montreal, Tatar is a great winger. He is so undervalued by so many out there. You are also asking for a chicago 2nd this year (probably a top 15 pick in the 2nd and a 4th this year for what a hopeful robby fabbri resurrection who is at best a bottom 6 option right now(potential sure but not on the right trend the last 2 years)? Joel Edmunson who played with Pietrangelo (one of the best defensemen in the league) On most teams is probably a bottom pairing guy unless you pair him with an elite defenseman (potential sure but not on the right trend the last 2 years.) Jordan Schmaltz who has 7 career points, and a 2nd rounder that is essentially a swap to get to chicagos 2nd. Montreal wouldnt trade away talent for a bag of crap. Not going to happen. Tatar would return schenn in a likely scenario if you wanted to do it that way but quantity does not equal quality here.
Sure a team could randomly give a 3rd rounder for a player in any given scenario. After that rinaldo deal from the bruins. Sweeney had a rough rookie year but Florida isnt giving up a 3rd and a 5th for a guy that was a healthy scratch for a bit of the year, was delegated to 4th line and had to play along a guy like RoR to actually contribute to the game. Blais also isnt anything special rinaldo is a good comparison for him. he had 4 points in 32 games. Sanford is young and could develop but most gms wont trade a 3rd for a young guy that is essentially a .33 point per game player.