Hi denlor2,
Welcome to the Mattress Forum! 
Most people that are looking for an “organic” mattress or materials are usually concerned more with “safety” than whether the materials have an actual organic certification and they usually aren’t aware that an organic certification isn’t the same thing as a safety certification. There is more information about the three different levels of organic certifications in post #2 here and some of the benefits of an organic certification in post #3 here and there is more about the different types of organic and safety certifications such as Oeko-tex, Eco-Institut, Greenguard Gold, C2C, and CertiPUR-US in post #2 here and more about some of the differences between organic and safety certifications in post #2 here and there are also some comments in post #42 here that can help you decide whether an organic certification is important to you for environmental, social, or personal reasons or whether a “safety” certification is enough.
I’m sorry, but your descriptions of the mattresses you’re considering aren’t complete, and I think that you may have ILD confused with density.
With your first mattress, I can’t tell the actual configuration of the mattress from the information you’ve provided. You’ll want to list the thickness of each layer, the style of latex (Dunlop or Talalay), the ILD/plushness (if available), and the blend (synthetic, natural, or blended) for sake of comparison.
With your second mattress, I think you may be listing the ILD instead of the density (lb/ft3) of the product. Assuming this, it seems this mattress has a 4" core of 40 ILD (firm) latex, followed by two 2" layers of 30 ILD latex, on top of which is a 2" layer of 20 ILD latex. You don’t list the type of latex or the blend.
Having a higher BMI presents special challenges and generally requires firmer materials (in the support layers especially). This could be firmer latex. The same overall guidelines apply with higher weights though that PPP (Posture and alignment, Pressure relief, and Personal preferences) along with using high quality durable materials that will maintain their feel and performance for longer periods of time are the way to make the best choices. Heavier people in general will need firmer and thicker comfort layers and firmer support layers than those who are lighter and because no materials will last as long with much higher weights the quality and durability of the materials and components is even more important than normal. I wouldn’t “rule out” latex mattresses for a higher BMI, and I would base your choices on your own personal testing (if possible). Post #3 here has more information and suggestions about heavier weights that is worth reading.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs, options, and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else. Their detailed knowledge of their mattresses and how they fit with higher BMIs, along with a customer base of many people that they can use as reference points, and any exchange, return, or any options they have available to customize a mattress after a purchase can help lower the risk of an online purchase.
As I listed previously in my reply, I don’t have enough information about this mattress to offer any sort of educated analysis of the product. If you can post back with more complete details, I’ll do my best to help with answering this question.
You’ll always want to contact any manufacturer with whom you’re dealing to become familiar with their warranty requirements for a foundation. Some people do place a thick piece of plywood over an old coil box spring, but this can still have the potential for sagging over time. If you do so, you may also wish to consider the use of a coir bed rug or something similar on top of the plywood to allow for air circulation. And also check to make sure that your bed frame has the proper center support.
Phoenix