Hi tempured mad,
I can’t make any specific suggestions because I can’t feel what you feel or see you sleeping on your mattress but I can make some general suggestions and link you to more information that may help with the detective work or trial and error that may be necessary to help resolve some of the issues you are having.
A good place to start is post #2 here and the posts it links to which has more information about the more common symptoms that people may experience on a mattress and some of the most likely reasons for them.
As you know you are in a somewhat difficult position partly because of the difference between you in terms of your size and weight (see the first part of post #2 here) and also because side/stomach sleeping is the riskiest combination in terms of sleeping positions because side sleeping tends to need thicker/softer comfort layers to relieve pressure points and stomach sleeping tends to need thinner/firmer comfort layers to reduce the risk of the pelvis sinking in too far and sleeping in a swayback position which can hyperextend the lumbar and lead to lower back pain. If your comfort layers in combination with a topper are too thick or soft it may work well for relieving pressure but it may be too thick/soft for your stomach sleeping. The best approach is generally “just enough” in terms of thickness/softness to relieve pressure when you are side sleeping so that you have the least possible risk of alignment issues when you are stomach sleeping.
It may also be a good idea to try a body pillow which can help avoid stomach sleeping because it can provide you some of the “comfort” or familiarity of having something against the front of your body while you are sleeping on your side.
You may need to experiment a little with thicker or thinner pillows since it’s possible that neither one of the pillows you tried may be ideal. There is more information about pillows in the pillow topic here.
[quote] I have also noticed I get pain in my elbows as well when I am on my back just before I fall asleep. I sink in and my elbows don’t so there is pressure that is placed on them.
I don’t know what to do here. Tempurpedic I sink in too much and get hot and can’t move so I wake up in middle of night. The topper fixes most of those issues but creates elbow issues for me.[/quote]
Your elbow issues are unusual and it’s very unlikely that it would be a pressure issue with a soft latex topper so it’s more likely that it could be some kind of a postural issue and that somehow your elbow is twisted or hyperextended or outside of its neutral range of motion.
It’s possible that the topper you chose is a little too thick and you may need a thinner topper so you aren’t sinking in as much.
A 3" 19 ILD topper is fairly thick and soft for stomach sleepers and it’s also very possible that the topper you chose is a little too thick for her as well.
It may be an idea to try turning your mattress over and adding the topper on the firmer side. While it still may not be the best solution … it may be useful to see how your symptoms change which can act as a reference point and “pointer” to the type of changes that may help resolve the issues you are having.
In very general terms when you may need to do some detective work and trial and error to resolve the symptoms you are both experiencing it’s also a good idea to make sure that any topper you purchase has a good exchange/return policy so that you still have options available just in case it doesn’t turn out as well as you hoped for.
I would probably sell the mattress to recover what you can before burning it (although I know it was more of a “frustrated” comment than a serious comment) 
If your mattress has visible impressions that are more than the warranty exclusion after you have been off the mattress for a few hours then you may qualify for a warranty replacement. You can measure the depth of the impression by putting a straight edge or a tight string across the area of the impression and measuring how deep it is. If the impression is 3/4" or less (which is Tempurpedics exclusion) then you wouldn’t qualify for a warranty replacement and if it’s greater than 3/4" then a warranty replacement may be worth pursuing.
As I mentioned earlier I can’t make any specific suggestions because you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved for anyone to be able to predict or make a specific suggestion or recommendation about which mattress would be the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own personal testing or sleeping experience (see mattress firmness/comfort levels in post #2 here).
Having said that I would avoid any preconceptions about which of their mattresses may be the best “match” for both of you based on any “theory” and I would make sure you do some very careful and extended testing in the store (using the testing guidelines in the tutorial post) so that you have good confidence that the mattress you are choosing has the best possible chance of success.
Phoenix