The u.s. and Canada have a demilitarized border. This would be bad for the u.s. if we went to war with Canada. However, we don't plan to go to war with Canada, so we aren't basing our decisions on that outcome.
Your claim is essentially there's no line, or that there is not a spectrum or that that line is beyond any economic measures. But there's no proof of that, so the logic in your "proof" is circular because your proof predicates on you knowing exactly where the line is (or isn't), when the location of the line is the thing to be proven.
I am saying that it unlikely to be reached and my personal opinion is we are moving further from it not closer.
I'm also saying that Russia is not making decisions as if it will be crossed. They are doing the exact opposite, making decisions assuming that they will not be forced out and will not get the reserves back.
I don't think they would realistically get the foreign reserves back even if they left, so that isn't much of an incentive.
The US and EU have to much politically at stake to hand them back, even if they leave. It would be seen as letting Russia get away without consequences for the invasion.
Time will prove one of us wrong. In 5 years Russia will either be occupying Eastern Ukraine or not. They will either have control of the foreign reserves back or not.
Plus, they aren't planning to leave Ukraine, so they aren't planning to get it back
Therefore the money is a sunk cost and not leverage. Therefore finical penalties don't matter.