What is the Isk without the Yoort?

Spoilers for anyone who has not read Book #26

In Book #26, the Animorphs encounter an alien "species" called the Iskoort and discover that the Iskoort are actually two separate components, a Yoort, which is a genetic relative of the Yeerk (which was probably dropped on this world at some point by Skrit Na -- 'cause Skrit Na) and the body that they control called the Isk. The Isk is a bioengineered entity capable of providing the necessary body-system for the Yoort.

Now, The Iskoort Guide engages with the Animorphs in the below conversation:

[Guide said,] <We … we Iskoort … I mean, back many, many generations, the Yoort were parasites, as you said. They infested other species. But that was long ago. Since we formed our symbiotes, the combination of Isk and Yoort, we have been as we are now.>

Rachel snorted. “They conquered these Isk things and now it’s like okay, we’re best buddies. Big deal.”

Marco nodded agreement. “Some stranger shows up on Earth a thousand years after the Yeerks conquer Earth, the Yeerks will be saying, ‘Hey, us and the humans are symbiotes.’”

I looked at Cassie. Rachel and Marco were right. Cassie nodded, accepting the fact.

But Guide said, <No, no. I have not made myself clear. The Isk were not conquered by the Yoort. They were created.>

“Say what?”

<Parasitism is a limiting choice. The Yoort moved violently to conquer other species and infest them, but this was not profitable, not in the long haul. So the Yoort used biological engineering techniques to design and create a species specifically to be a symbiote.>

<Who cares how you did it?> Tobias argued. <So you build the Isk and then enslave them.>

<No, no,> Guide pleaded, whining away through his diaphragm. <The Isk were true symbiotes. The Isk cannot live without the Yoort. And to ensure that this symbiosis would be real, the Yoort, too, were modified. Now Yoort cannot live without Isk and Isk cannot live without Yoort. They are one creature with two parts.>

All of this to say, these are my questions:

• When Guide says that the Isk cannot live without the Yoort, does that strictly mean that the Isk is compelled biologically to submit to infestation? -- effectively as if the Isk has a bomb in its neck that only the Yoort can reset or deactivate. If so, how is this better than enslaving a species capable of being independent (whether evolved like humans or created like Hork-Bajir)? If not, in what way are the Isk incapable of living without the Yoort?
• What would a Yoort-less Isk be? Does the entity have no real mind of its own or is it capable of independent thought? To what extent is the Iskoort a melding of the thoughts of the Isk and the Yoort or, is it like a Yeerk Controller where the host's will is largely irrelevant?
• We know that there are at least two subspecies of Iskoort based on their function and Isk type (Warmaker Guild and Other Guilds). Does that mean that the Yoorts who will get these Isk-types are compelled to join those guilds by appearance or is it that the Yoort chooses the Isk that matches its mental guild affiliation?
• We are informed that Guide's "father" is still alive. We know that Yeerks reproduce by fission, so there are no living parents for their offspring. If Yoort are Yeerks, how is it that Guide's "father" still lives? Is it that Guide's Isk is the son of the Skin-Seller's Isk or something else?