Not at all; I thought it was a pretty good exegesis! 
Some additional things (not many, though, since you did a great job already):
1.) I would say that “the creation” is not restricted only to “the heathen” (although on the other hand, the two terms are actually rather interestingly interrelated in regard to this topic–but that’s another discussion). “The creation” is everything–the total scope of all not-God creation. (The paragraph of Rom 8:18-22 is one of the several Big Themes underlying the fantasy series I’m supposed to be editing this summer instead of doing much composition here on the forum… 
)
2.) As Jeff says, the larger scope (particularly regarding Israel as the usual archetype of rebel against God, through chp 11) shows that in fact God is working for the good to those who, at the moment, are stumbling over Him, too.
3.) The problematic verse, 28, is notoriously difficult to translate, and shows up in two distinct versions in the textual record: one with {ho theos} following after {sunergei} (synergy, as we would say), and one without {ho theos}. Both readings have ancient and noteworthy witnesses in the textual record, but the shorter reading has a much more diversified support among textual families. Also, it is easier to explain the addition of {ho theos} as an explanatory gloss–since {sunergei} can be taken to imply a personal subject, and since authorities may have worried in pagan Mediterranea that readers would understand Paul to be talking about Nature personified as the bride of God, i.e. “all things”, working together for good to those who love God. (It’s one thing to use a mother-figure in labor as, y’know, a colorful metaphor; and another to imply that “the creation” is somehow a person actually acting as God’s agent.)
This is probably why my older version of the NASB (not sure about newer revisions) goes with the inclusion of a second {ho theos}, over against the decision of the USB editors, whom otherwise they usually follow. (The variant is still represented in the sidenotes as "some ancient mss read, “all things work together for good”.)
Another reason to go with the shorter reading, is that it makes at least a little more grammatic sense in the sentence.
But, on the other hand, the immediately following sentences are all about the action of God: those whom He foreknew, He also predestined, that He might be the chief (first-born) among many brethren; and whom He predestined, He also called; and whom He called He justified and also glorified. So there is some rationale there for reading {ho theos} (the God) back into verse 28 as the implied doer of action in working-together.
Green, unsurprisingly, tries to have both uses of “God” in the sentence; but then, surprisingly, doesn’t follow the textual version in his actual Greek. So his literal translation reads, “But we know that God works together all things for good to the (ones) loving God, to the (ones) being called according to His purpose”.
But his super-literal translation goes with the actual text on his page (which happens to follow the USB this time).
So, in Greek (with [square brackets] indicating the probable glossed addition, not found in Green’s or the USB’s textual representation):
{oidamen de hoti tois agapo_sin ton theon panta sunergei [ho theos] eis agathon tois kata
we know And that the (ones) loving God all things together [God] for good the (ones) according to
prothesin kle_tois ousin}
purpose called out being.
The reader should be able to see why translators would be inclined to pull out their hair and make broad guesses as to what exactly is being written here, even without the inclusion of {ho theos} as a supposed subject of the sentence.
Does {de} (a weak conjunction) mean ‘and’, ‘but’, ‘yet’ or a more general ‘now’? (I’ve seen translations each way.) Does {tois} mean ‘the ones who’, ‘those’ ‘these’? Does {panta} really mean ‘all things’ collectively, or ‘all’ in some more abstract way? What the heck is the subject of the sentence? Is there only one sentence, or two? Do the two parts make one sentence, two sentences, or are they actually connected to the preceding and subsequent material respectively? Does {sunergi} mean ‘together-acting’?–‘together-working’?–only ‘together’? (Probably not the latter, I would say, but Green ignores the {ergi} portion, for example, in his super-literal translation.) Heck, does it mean ‘fellow-worker’?! (as in 1 Cor 16:16:) Does {eis} mean ‘for’, or ‘into’, or ‘to’? (Or maybe even ‘toward’, like {pros}?) The usage of {agapo_sin} and {agathon} in the two clauses, looks suggestive as cognates of each other, but does that mean anything special? Does {kata} mean ‘according to’, or some other more basic meaning such as ‘down’? Does {kle_tois} mean ‘called out’, or ‘called these/those’ or ‘these/those called’, or just ‘called’? (Probably not the latter, I would say.) {ousin} is some sort of actionable verb, right? But how does that fit into anything? Does {prothesin} (i.e. a grammatic object form of {prothesis}) mean ‘purpose’, and if so in which way? Or does it mean the cakes of bread in the front part of the tabernacle, which in theory may only be eaten by priests but of which Christ pointed out that David and his men, when hungry, ate them on the sabbath and did not sin!?!
AAAHHHHHHH!!! … … just… write down anything, okay? We’ve got a lot of Bible to translate. Whatever sounds good in our theology already, that’ll work. Add another reference to God if that helps.
I’ll let other people go hunt up various translations for it, or make some educated inferences themselves. I have my own guess, but I’ll save it for later. 
Busyness is occurring back here at the office…
ETA: none of which should be considered to take away from Jeff’s fine analysis. 
Mainly the big discussion was to explain why in the middle of this great suggestively universalistic language, there’s this weird throw-off sentence.
).
LOL