This handbook has several good resources in it. I have gone through it carefully and have noticed some of the references are to the wrong books. Adding page numbers would
REALLY help. An example is Black lotus extract (CAdv98 updated from A&EG) not (DMG)
Also don't forget DragMag301 p58 for +2 to DCs
I also sugggest that the greensickness be DC35. It seems that Craft DC = Save DC + 2, if volcanic gas can be trusted though I still don't know how you got that DC (Sa 24,25 lists none). Its even close to the Black lotus extract cost.
What is needed is a regular to greater poison conversion. Wyvern poison might work for that. If craft and fort DC scale equally then it is craft DC = Save DC + 8. This makes sense as it is animal-based, more con, and an injury poison. Gargantuan wyvern poison's save DC is 21 so its craft would be
29. The reason I chose greater wyvern is that it has the same CR as the greensickness. So it is about as effective (once activated) as greensickness in terms of lethality. They are also 1k away in price. I understand that craft DC and poison DC are measure of different things but this does point to a more conservative Craft estimate of 30 or 35 rather than 40 or 45. To be sure though, we could do regressions on various classes of poisons.
Lastly a section on how to meet those Craft DCs would be awesome. Come to think of it the SRD seems to suggest that only a DC20 is needed (for superior or complex items):
When casting the spell minor creation, you must succeed on an appropriate Craft check to make a complex item.