Sorry, I can't see PS cutting through a Bijuu.
Sure, it cuts mountains, but Bijuus destroy mountains themselves most of the time.
Madara said only a Tailed Beast can surpass the lethality of his PS.
He faces six.
Hachibi was about to get stabbed by Madara in the scan I just posted, I don't see why they can't be bisected. A bijuu without a host maybe but a transformed Jinchuuriki doesn't have the same benefits. (Hence Madara almost stabbing Bee and killing him via a lvl 2 Susanoo)
Well, even if they can't be cut in half, they can still take damage and there's also the chakra receivers. Madara's sword swings could damage and destroy the chakra receivers.
Not really, no.
It's a fact that when you use clones you divine your power between yourself and the clones themselves.
2 clones? 2 50% Madaras.
3? 3 33% Madaras.
4? 4 25% Madaras.
That's the way it goes.
The baseless assumption isn't the part where you say clones weaken the user because that's obvious. The baseless assumption is that to make a few Mokuton branches he needs over 50% of his power.