Re: the extruded mass getting put into a big sloshy blob-
Actually, in #18 The Decision, an accident causes the Anis' consciousnesses to be shunted to their extruded mass. They don't end up as randomized, inside out blobs. In fact, they find themselves in what sure looked like their normal bodies. Everything was in the right place, including organs, bones, skin, and even their morphing outfits. After they are picked up by a passing space ship, they don't have any problems thinking, talking, walking around, or even morphing. The only complication is that whole "popping back into Z-space one by one" thing.
So there actually is some pretty solid canonical evidence that the extruded mass does not end up messed up and inside out. I worked out a pretty detailed theory based on this a while back, but I don't think I need to repost it here.
As for the question of whether a yeerk could leave a morphed host-I don't think that exactly happens in the series, but something kind of like it happens in the Hork Bajir Chronicles. When Aldrea refuses to demorph, Esplin comes up with the idea of infesting her and making her demorph, so he pops out of his host and crawls into her ear. Esplin gets pulled out before he can try this, so we don't know if it would have actually worked. Come to think of it, Esplin probably didn't know either.
And yeah, this is pretty confusing. My head's starting to hurt a little too.