Habitude is qualitative ordering of the nature of some subject either well or badly to some act out of several possibles, through mutually disposing several things. As a quality, it requires a subject, and therefore Aquinas considers a number of questions concerned with the kind of subject for which habitude is an appropriate quality; since accidents are defined in relation to the substances that can have them, doing this clarifies several aspects of the definition. Rather than translate the whole question, as I did for the defining questions, I will make some comments with a few translations of select passages.
Can bodies have habitudes?
Aquinas argues that it depends. Habitudes dispose either to form or to operation. Habitudes always need to distinguish out some act out of several possibilities; bodies on their own are only determined to one operation, so bodies on their own develop no habitudes toward operations. However, habitudes to operation in the soul can be in a body secondarily, "inasmuch as the body is disposed and enabled to devote itself readily to the workings of the soul" (ST 2-1.50.1).
If, however, we speak of the disposition of the subject to form, then habitual disposition can be in body. And in this way health and beauty, and suchlike, are called habitual dispositions. But they do not completely have the notion of habitudes, because their causes are by their nature easily transformable.
In the reply to the second objection he further clarifies this by suggesting that health and beauty are habitudes comparatively -- they are 'difficult to change' relative to most things we consider dispositions -- but habitudes in the soul, like knowledge and virtue, are 'difficult to change' simply. I take it that the point is that bodily habitudes have a greater measure of dependency on things other than themselves than habitudes of the soul; that is, the difficult-to-change and the easy-to-change is a measure of relative independence.
In what way do souls have habitudes?
The soul does not naturally have a habitude to nature, because that would require something to which it is further disposed; this contrasts with the body, which has a habitude-to-nature with respect to the soul. However, importantly, this also means that under the right conditions, the soul can have a habitude to a higher nature than itself; this can occur by divine grace, for instance, which gives us a habitude to the divine nature. In this way, the habitude takes as its subject the essence of the soul.
The usual way the soul has habitudes is by having habitudes to operations, which are themselves based on powers or capabilities. In this way, the habitude takes as its subject the powers of the soul.
Whether nutritive or sensitive powers of the soul can have habitudes?
Nutritive and sensitive powers are not in and of themselves capable of multiple possibilities because they "work from natural stimulation" (ST 2-1.50.3), ex instinctu naturae. Therefore, simply considered in themselves they do not have habitudes. However, rational powers are capable of multiple possibilities, so we can have habitudes in other powers of the soul insofar as they "work from command of reason".
On the basis of this, Aquinas concludes (ST 2-1.50.3 ad 1) that nutritive powers, which do not obey the command of reason, have no habitudes, but sensitive powers can obey the command of reason, and therefore can have habitudes. This is certainly true of human senstive powers, which are ordered naturally to rational powers; but what about the sensitive powers of animals other than human beings?
To the second it must be said that sensitive powers in brute animals do not work from the command of reason, but if brute animals are left to themselves, they work from natural stimulation, and thus in brute animals there are not any habitudes ordered to workings. There are nevertheless some dispositions in them ordered to nature, such as health and beauty. But because brute animals are through a sort of custom disposed by human reason to some working or another, in this way in brute animals habitude can in a certain way be put; thus Augustine says in the book of eighty-three questions, that we see the most savage beasts being restrained from that in which they have the greatest pleasures by fear of pain, and when this turns into custom for them, we call them tamed and gentled. However, the notion of habitude is incomplete as to voluntary use, because they do not have lordship of using or non-using, which it seems pertains to the notion of habitude. And therefore, properly speaking, in them there cannot be habitudes. (ST 2-1.50.3 ad 2)
'Use' is a technical term for St. Thomas; it is a particular act of will, the application of a thing to an operation; we are doing it when we apply a horse to riding or a stick to hitting by deliberately selecting this end for it. In doing this, our will is acting as a prime mover. In ST 2-1.16.2, he had concluded (also in agreement with Augustine in the Eighty-Three Questions) that it is an act exclusive to rational animals. At no point so far has he actually connected habitude and volitional acts of use; it comes out of left field here, but I think his idea is that properly speaking the brute animal gets the quasi-habitude, or habitude in a loose sense, that we call 'tameness', through use by a human will, and therefore the selection out of multiple possibilities is actually extrinsic to the disposition here.
This is a point on which St. Thomas seems very much to be deviating from Aristotle; but, Aristotle's remarks being somewhat scattered, it's difficult to say how far. I think one can argue that he is not so much differing as to substance as making a terminological adjustment, so that habitude in a strict sense is more closely connected to intellect and will; trained animals have habitudes in an extended sense by their connection to intellect and will, which in their case is outside the actual disposition. This raises a few questions that are not an issue in Aristotle's somewhat looser terminology, such as those with tool-use in other animals. I suspect St. Thomas would give the same answer to such questions that he gave in 2-1.16.2 about beasts using their members, that they do this from natural stimulation (or instinct; the Latin instinctus is not as narrow as the English 'instinct'), and thus not from use in the proper sense. It is very clear that we need to distinguish rational habitudes from other kinds; rational habitudes on every point of the definition of habitude fit the definition more 'tightly' than other habitudes do. But it's at least arguable that we should see Aristotle's looser sense of habitude as a sort of genus, in which they can differ in precisely how the multiple possibilities are involved, and Aquinas as concerned with the primary species of that genus, those that have volitional use as part of how we understand the multiple possibilities.
While Aquinas flatly denies habitude in nutritive powers, the allowance of a habitude-in-a-broad-sense in the case of tame animals also raises the question of whether there might not be possible something similar in nutritive powers in plants (through horticulture) or in animals (through veterinary medicine).
These sorts of questions arise, I think, from the fact that St. Thomas does not give extensive explanations for some of his reasons, so there are unstated gaps. My guess is also that St. Thomas that, since in context he is building up to a discussion of virtues, the most proper habitudes, that he is really just thinking about virtue in these discussions, and thus not fully following through on the lesser questions of how this relates to the various roles dispositional qualities take in explaining animal behavior.
Intellect and will are in any case the primary and most proper subjects for habitudes, and thus should be kept for their own discussions.