Can someone explain the skeleton physics to me?

Argh, I can’t for the life of me get my physics ragdolls working the way I’d like. No matter what I do, my skeleton is much ‘floppier’ than I want it to be.

My first question is about the bone locators. When I import them, the x is facing in the wrong direction as you can see here:

Is this a problem? I’m wondering if it is leading to my problem of the constraints not seeming to have an effect on my joints.

Which is the problem I can’t wrap my head around. No matter how I play with the angular limits, the stiffness and damping settings - I just get a really floppy fish (which brakes the mesh). The best result I could get was locking all the angular limits, but I’d like a little more movement than that. I’ve tried low number and ridiculously high numbers in all the sections: stiffness, damping, angular damping - and I’m not seeing much of a difference.

Basically, I’d like a fairly stiff skeleton with just a little spring in the joints. Also, I’d prefer the skeleton not swing apart when a heavy force is applied (stretching the mesh out) - I don’t really want any translational or rotational ‘give’ beyond the limits I set. As of yet, I have not been able to get anything like that.

Are there any good guides that go into detail on what each setting does? Can anyone provide some insight? I’m perplexed…