Hi palla,
There are too many unknowns, variables, and personal preferences involved to be able to predict which mattress design will work best for any specific person based on specs (either for the person or the mattress) or theory at a distance. When you can’t test a specific design in person (or something that is very close to the same) then the best way to choose the combination that you believe would work well for you would be more detailed conversations with a knowledgeable retailer or manufacturer (see mattress firmness/comfort levels in post #2 here which also includes links to some “generic” information but isn’t specific for any person).
If the slats are 3" or less apart then this should certainly work well.
I would make sure you’ve read post #15 here about building a DIY mattress to make sure you have realistic expectations about the success of your initial choices and the trial and error that may be involved. The most effective approach for building a DIY mattress is a “spirit of adventure” where your experiences and the satisfaction that goes with the DIY process itself and what you learn along the way is more important than any cost savings you may or may not realize which will depend on how well your initial choices work out and whether you need to purchase any additional layers to “correct” any choices that turn out to be less than ideal for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
Having said that … I think your overall approach is a good one … especially since you are used to sleeping on the floor. This way you can build your mattress from the “bottom up” and use your experience on the previous step to help you decide on what (if anything) needs to be added to your previous layering. While you really aren’t adding a topper since it will all end up inside your cover when you are done … post #2 here and the topper guidelines it links to may be useful to help you decide on the thickness and firmness of the comfort layer that may work best for you on the support core you start with.
Both Talalay and Dunlop have been used for decades although Dunlop was introduced in 1929 so it’s a little older than Talalay which was introduced in the late 30’s (see post #9 here). Both manufacturing processes have a long history behind them.
Your configuration would be the opposite than many people would choose (Talalay is more common in the comfort layers because it is more commonly available in softer and more pressure relieving versions and Dunlop is often used as a support core because in the same ILD it has a higher compression modulus and is more “supportive” than Talalay) but all of these types of choices are a personal preference and there really isn’t a “right or wrong”. There is more about the different types and blends of latex in this article and in post #6 here.
The most effective way to know how you feel about latex itself or which of the different types of latex you may prefer would be with your own personal testing. Latex works very well on an adjustable bed because it’s very flexible (and very heavy) and it should work well on your futon lounger as well.
This sounds like an interesting project as well. It may be difficult to quilt the wool to the cover without a quilting machine or unless you have some expertise in making wool quilted covers.
I certainly think highly of Ken at Arizona Premium and they are a great source for components and expertise. The component post here also includes some additional sources for latex of different types and blends.
Good luck with your DIY project and I hope that things work “perfectly” for you with your initial choices which of course is always the ideal :).
Phoenix