I don't think the calculator is accurate for movements within the top 10, probably due to a lack of sample size.
Trade downs in the top 10 are very rare and the reason they are very rare is because the cost demanded is often exorbidant, unjustifiably so in most cases.
Part of it is human nature. The regret of missing out on their BPA by moving down for an extra pick overpowers the logical part of the brain.
If we trade down with Calgary and go from 7th to 9th, it would certainly cost at least the 41st OVR pick with no addition from the Sens. If anything they'd probably demand the 28th OVR.
My intuition on this is the same as what you outlined.
Tanev
We may need to go 4 x 4.5M to get Tanev.
I would do it, knowing it will be a buyout in years 3 or 4, because winning this year is very important (according to a league executive) if we want to keep Tkachuk.
We need to make the playoffs and create some magic. With the rising cap, buying out the final year of the contract won't be too bad.
I still think that no one is going longer than 2 years at 4.5M+, but I could be wrong.
Sure, though I think Pesce does that too
The potential advantage of Tanev, is it allows us more flexibility like upgrading Joseph,
I mean, I am sure they would love to get Pesce, but I don't think it's realistic.
The only reason Tanev is realistic is because he is 34 years old, so we can leverage against our undesirableness as a destination by overpaying him in term.
The problem with Pesce is that multiple teams will line up to give him full term and top dollars. So at that point it's less about money and more about choosing his ideal destination.