There is so much here to digest, I'll try to narrow down my comments and questions as much as possible to help wrap my head around things. (Cassius, your comments on pleasure are quite interesting and could make another thread in themselves!) For the most part I totally understand and agree with the points made. I'd like to focus on 1) an infinite system, 2) chance, and 3) isonomy.
1) In EP, the number of atoms is infinite. The types of atoms are innumerable. If my thinking is correct, the types of combinations of atoms would therefore be innumerable but not infinite (innumerable type x other innumerable type = seriously innumerable). If the types of combinations were mathematically infinite (although it could be said that, practically speaking, they are infinite) then the probability of any given thing existing in the universe would be 100% and if I'm not mistaken this doesn't seem to be the case in EP.
2) Regarding chance, my understanding is that chance is involved in the combinations of atoms. Once compounds are formed there are properties that affect future combinations, but as a general idea chance is a factor in the Epicurean universe (but not in the life of a wise man). If it were not a factor, then all would be by necessity and such is not the case.
3) Isonomy is where I get completely confused. DeWitt lists three aspects of isonomy: "first, that in an infinite universe perfection is bound to exist as well as imperfection; that is, 'that there must be some surpassing being, than which nothing is better'; second, that the number of these beings, the gods, cannot be less than the number of mortals; and third, that in the universe at large the forces of preservation always prevail over the forces of destruction."
DeWitt also mentions an isonomy of values as well as of things. Perfection and imperfection are values, but they are ideas of man and at the scale of man and not at the scale of the universe, to my understanding. Otherwise, wouldn't they be Platonic Ideals? And how can "equitable apportionment" occur in a chance system? Is the reason for more gods than mortals because the forces of preservation must exceed the forces of destruction in an everlasting universe? I'm completely on board with his third premise of preservation exceeding destruction. My understanding, however, is that that would apply only to the atoms. All else is compounds and is subject to dissolution.