Hi missy,
You are very light which generally means that lower ILD latex would tend to work better than firmer latex. A total of 4" of softer latex (both 19 and 24 ILD latex would be quite soft for most people) could be a little on the thick/soft side and “risky” for some back sleepers but with your lower weight it may work quite well (the 24 ILD would act as a transition layer more than a comfort layer) but your own personal testing would say more than “theory”. How did you find the mattress at Verlo for pressure relief and alignment? Your experience with this could be a reasonable guideline for a “choose your own layer” mattress.
I’m guessing you mean polyurethane or memory foam here? Latex (both blended and all natural) is also foam and padding of course but they are both OekoTex standard 100 class 1 (safe for babies) certified. The 100% natural Talalay has all natural latex but is also more expensive and likely to be a little less durable and pressure relieving in the softer ILD’s. 100% natural Dunlop is perhaps the “purest” form of latex but is also firmer and doesn’t come in layers that are as soft as Talalay which may be important to you.
I’m not sure if I understand the layering of the Lebeda you mentioned. Was it just 2 x 4.25" layers of latex with an ILD of 28 with no polyfoam in the quilting? This seems to be an unusual layering and doesn’t seem accurate but if it is it may be a little on the firm side for you for pressure relief but again your own experience would be more accurate than “averages”.
Some of the best online manufacturers that are members of the site and make and sell high quality and value mattresses are listed in post #21 here. Several of these sell layered zip cover mattresses.
Post #2 here includes the better options within reasonable driving distance of Peoria (and I see you’ve already fond the ones that are closest)
Hope this helps but if you have more questions feel free to post them 
Phoenix