As to your question about how many drawings to put in a page, it comes down to how much each individual drawing requires, as limiting how much space a drawing is given can impede our brain's capacity for spatial reasoning while also making it harder to engage our whole arm from the shoulder. The best approach to use here is to ensure that the first drawing on a given page is given as much room as it requires. Only when that drawing is done should we assess whether there is enough room for another. If there is, we should certainly add it, and reassess once again. If there isn't, it's perfectly okay to have just one drawing on a given page as long as it is making full use of the space available to it.

As far as I'm concerned, you do this just fine. You may stick to just one drawing per page, but you're still making good use of the space available to you.

Jumping in with your organic forms with contour curves, you're generally doing a great job of sticking to the characteristics of simple sausages as per the instructions, except for the left side of the second page, where you've got one shaped as an ellipse (which very much contradicts those characteristics of simple sausages. The one below it is mostly okay, but one end is visibly smaller than the other. Then the one to the right of that is similar, but steadily better, with the upper right on that page being fine.

Oh, one other thing to remember is that as we slide further away from the viewer along the length of a cylindrical form, the contour curves should be getting wider, as per what's explained in this video from Lesson 1. You do generally keep the degree roughly consistent, so keep an eye on that.

Continuing onto your insect constructions, there's a lot here that you're doing very well. I can see a great deal of attention being paid to considering how each individual form you draw is three dimensional and solid - although there are little shortcuts that you take sometimes that undermine that solidity. So in a sense, it's not a matter of doing things either right or wrong - it's that you're doing things very right, and then on top of that there are actions that you take that occur more in the 2D space of the page, which undermine the strengths that also try to exist alongside these issues.

I'm sure that's about as clear as mud, so let's talk about it a bit further.

Because we're drawing on a flat piece of paper, we have a lot of freedom to make whatever marks we choose - it just so happens that the majority of those marks will contradict the illusion you're trying to create and remind the viewer that they're just looking at a series of lines on a flat piece of paper. In order to avoid this and stick only to the marks that reinforce the illusion we're creating, we can force ourselves to adhere to certain rules as we build up our constructions. Rules that respect the solidity of our construction.

For example - once you've put a form down on the page, do not attempt to alter its silhouette. Its silhouette is just a shape on the page which represents the form we're drawing, but its connection to that form is entirely based on its current shape. If you change that shape, you won't alter the form it represents - you'll just break the connection, leaving yourself with a flat shape. We can see this most easily in this example of what happens when we cut back into the silhouette of a form.

So for example, here on this wasp where you have indeed put a good deal of consideration into the solidity of many of your forms, you end up cutting across them where I've marked in red, and you also end up with cases where you'll extend off those silhouettes with flat/partial shapes.

Instead, whenever we want to build upon our construction or change something, we can do so by introducing new 3D forms to the structure - forms with their own fully self-enclosed silhouettes - and by establishing how those forms either connect or relate to what's already present in our 3D scene. We can do this either by defining the intersection between them with contour lines (like in lesson 2's form intersections exercise), or by wrapping the silhouette of the new form around the existing structure as shown here.

This is all part of accepting that everything we draw is 3D, and therefore needs to be treated as such in order for the viewer to believe in that lie.

You can see this in practice in this beetle horn demo, as well as in this ant head demo. You can also see some good examples of this in the lobster and shrimp demos on the informal demos page. As I've been pushing this concept more recently, it hasn't been fully integrated into the lesson material yet (it will be when the overhaul reaches Lesson 4). Until then, those submitting for official critiques basically get a preview of what is to come.

The other point I wanted to call out is in regards to leg construction. In essence, you appear to follow the sausage method to varying degrees - sometimes you'll employ the characteristics of simple sausages, but sometimes you'll switch more to ellipses. Sometimes you'll focus your contour curves at the joints between them, sometimes you'll add additional ones through the midsection. Long story short, give the sausage method diagram another read.

The key to keep in mind here is that the sausage method is not about capturing the legs precisely as they are - it is about laying in a base structure or armature that captures both the solidity and the gestural flow of a limb in equal measure, where the majority of other techniques lean too far to one side, either looking solid and stiff or gestural but flat. Once in place, we can then build on top of this base structure with more additional forms as shown here, here, in this ant leg, and even here in the context of a dog's leg (because this technique is still to be used throughout the next lesson as well).

Now, as to your other two questions:

I feel like I had the most trouble with form segmentation (like laying the shell on top of the form for the cockroach)

For this, while the form is rounded, it can help to think about how it can be divided into top/side planes, as shown here. We can then consider these planes as we draw our segmentation, as shown here.

and the legs, especially the long spindly kinds like spider or ant legs

Drawing really skinny sausage forms is hard. The more we draw the sausage forms (even when they're not super skinny), the better we get at them. So, being sure to give ourselves ample room on the page to work through those forms, and of course investing a lot into the magical ingredient of practice, will help make it easier over time.

And with that, I'll go ahead and mark this lesson as complete. You can of course continue to address the points I've raised here throughout your work on the next one.