Very good question, here's a quick tutorial to static joints
Joints in Toribash aren't as stable as one might want, especially when you start to merge several objects together or tilt the objects with the rotate tool.
All overlapping objects need to be connected to eachother to not push eachother apart like this:
In the first example we have 3 objects going through eachother.
Object 1 and Object 2 are connected
Object 2 and Object 3 are connected
Object 1 and Object 3 are connected
One could think having the first two joints would be enough, as it links all the objects together.
However, since the objects are overlapping we also need the 3rd joint
connecting Object 1 and Object 3, or else these two would push against eachother and deform our sculpture(example .tbm below
As seen here adding just one more object will increase the joints required by 3, as the new object needs to be connected to every other object, or else they would push eachother away.
When we start rotating objects things get a little more complex.
If we want to rotate an object on the Y axis (left/right), like I have done in lw_sabertooth for example, we need the axis setting for the joints connecting the rotated object to the rest to look like this:
This also applies to rotation on other axis.
If you do not set these settings correctly the joints will make the objects try to snap back to the default rotation
As for objects seperating when swung quickly, there is no solution for this that we know about. Sadly this "feature" is embedded deeply in Toribash's sourcecode and until a dev decides to fix it there is nothing we can do about it
I hope that answers all of your questions regarding static joints, let me know if not.