Hi William17,
Welcome to the Mattress Forum! 
I hope the information presented here is useful. Be sure to take a few minutes and read through the mattress shopping tutorial to assist you as you go through the mattress buying process.
I’m sorry your current mattress is breaking down so soon.
A higher BMI presents special challenges and generally requires firmer materials (in the support layers especially). This could be firmer latex or innersprings (the type of support component would be a personal preference and in the right design either could be suitable) or even a zoned construction. 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” any types of mattress and base your choices on your own personal testing. Post #3 here has more information and suggestions about heavier weights that is worth reading.
You’d certainly be considering an item that used higher quality materials with the hybrid model. For the best advice as to whether the 3" of latex would “be enough” for you, I suggest a phone call to mattresses.net (a site member here, which means that I think highly of them and their advice and products) and explain to them your current situation and what you’re attempting to accomplish. Their detailed knowledge of their mattresses and how they fit with different body types and sleeping positions along with your feedback from any local testing, 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. These online retailers or manufacturers can also be a good “value reference” for local purchases to make sure that if you are paying a “premium” for a local purchase (in exchange for the kind of “in person” guidance, service, and value that comes with dealing with a local retailer that can help you make more “accurate” choices that you have tested in person) is not too high.
If you wish to look at some items locally (near Kansas City), subject to first confirming that any retailer or manufacturer on the list you wish to deal with is completely transparent (see this article ) and to making sure that any mattress you are considering meets your specific criteria and the quality/value guidelines here … the better options or possibilities I’m aware of in and around the Kansas City area are listed in post #2 here .
I’ll look forward to learning about your progress and any other specific questions that you may have.
Phoenix