Hi iheartsleep.
Welcome to our Mattress Forum! 
When buying a mattress I would always make sure to check that the foams used in the mattress have a basic certification for the harmful substances, so at least you have the assurance that the smell and off-gassing isn’t harmful although some people can still be sensitive to it. This way you have some assurance than the VOCs are below the testing limits for the certification (see post #2 here for more information about some of the more reliable “safety” certifications). If the materials in a mattress or the mattress itself has a reliable “safety” certification then for most people they would certainly be “safe enough” … regardless of the type of material or the name of the manufacturer on the label.
Both Sleep On Latex and SleepEZ are using good quality and durable components in their mattresses with all the foams having reliable “safety” certifications. While I can’t speak to whether any of them would be a good “match” for you in terms of comfort, firmness, and PPP (Posture and alignment, Pressure relief, and Personal preferences) as this depends so much on your own careful testing I would certainly strongly rely on the many years of knowledge, experience, and guidance that they offer all their customers. I am glad that you already had a conversation with Shawn at SleepEZ as he is one of the most helpful, patient, and hardest working people that I know in this industry. As you may be aware both Sleep On Latex and Sleep EZ are members of this site and like all the members here I think very highly of them and consider them to be among the “best of the best” in the industry. They are both very good at giving guidance that can help their customers make the best possible choices out of the many options they have available based on their height/weight/body shape and sleeping positions and certainly you can call and talk with them about which of their mattresses may be best for your needs and preferences. Local testing on mattresses where you know the materials and layering can also provide some good guidance and can help them help you more effectively.
In conjunction with your doctors recommendations and treatment for the budging discs, having the proper support to keep your spine aligned to maintain the appropriate amount of space between the disks and the surrounding vertebrae in the cervical area is probably one of the “must have” and a base line in relation to any mattress you are considering and if you find the correct configuration this may help relieve some of the pressure placed on the vertebrae. This is once again a discussion for you to have with both of the manufacturers you are considering and depending on the BMI differential between you and your husband and also his sleeping positions, needs and preferences you may indeed need to look at a side split construction and if necessary after purchase customization. In combination with your mattress, one other thing to look at would be your pillow to make sure that when on your side it is of a sufficient thickness to hold up your head and it assist you in maintaining proper neutral alignment throughout the night for your cervical/upper thoracic alignment. You’ll want to avoid too much flexion or extension, and if you change positions throughout the night (side to back, for example), some people prefer a pillow that is “shapeable”, such as down, natural fibers or shredded latex. I go into a bit more detail about pillows in post #13 here , and you might find that interesting. Loft, support, comfort and temperature regulation are also other factors to consider. There is also a pillow thread here that you may wish to peruse.
Latex will certainly be a more supportive material then memory foam and depending of the plushness you decide on, it can still offer the cradle and comfort you need to relieve any pressure points. It would be well worth doing some local testing on a mattress that has latex in its upper most comfort layer and experimenting with a few firmness options. Now that “in theory” you narrowed down some preferred materials I would still recommend (as I do for all people that have more difficulty finding a mattress with the right “balance” between comfort/pressure relief and support/alignment or who have more challenging circumstances or sensitivities, body types that are more difficult to “match” to a mattress, more complex medical issues, or who have a history of having more difficulty in finding a mattress that works well for them) may be better off personally testing locally some mattresses before deciding on a purchase … especially if they are considering a mattress that uses materials that they aren’t familiar with.
I have decided to discontinue the provision of listings of potential retailers in various geographic regions (unless they are already approved site members), because of the difficulty in maintaining such lists in a retail landscape that is constantly changing, and most importantly the confusion it was creating with the consumer members who incorrectly assumed that these businesses had indeed gone through the strict qualification process and were approved as members of The Mattress Underground. Such an assumption is unfair to both the consumers seeking assistance, as well as the very businesses and manufacturers who have indeed qualified the be members here of The Mattress Underground.
Aside from that, I would always confirm that any retailer or manufacturer that you wish to visit is completely transparent (see this article) and also make sure that any mattress that you are considering meets the quality/value guidelines here.
You can perform a forum search on Birmingham or other cities near you to see what businesses have been previously discussed here on the forum in those areas.
If you have any questions about specifications or certain products, feel free to post back on the forum and I’ll do my best to provide answers.
Phoenix