Meanwhile the monarchs keep leaving more eggs on the what few leaves
are there.

Well, I haven't had this many caterpillars/butterflies in my own
garden, but it sounds like this is why you don't have any leaves.

I'm guessing you need more milkweed, and/or fewer caterpillars/eggs.
If you don't let the plant(s) retain some leaves, it might not make it
to whatever season doesn't have caterpillars (don't know what that is
where you are, but it looks like the migration is south in the fall
and north in the spring).

It doesn't sound like an issue with encouraging the plant to grow. It
seems like the plant is trying to (at the top rather than along the
stem, but that should be OK), but gets munched before it gets very far.

After fighting off the aphids, now there seems to be something turning
the leaves whitish and leaving some sort of spider web looking stuff
on them and they are dying.

Spider mites? If so, it seems like something as simple as spraying
off the plants with water might help, according to:
http://ohioline.osu.edu/hyg-fact/2000/2012.html

Maybe there are other things which cause this symptom.