Hello Fire_Water,
While I am not an expert by any means (that would be Phoenix), I would like to help and maybe see if we can clear the picture up. It sounds like you did something similar to what I was thinking of trying, but decided against due to a few reasons.
The image I am getting is that you purchased 4 mattress toppers and stacked them on top of each other to build yourself a bed, using the massage table as your foundation. I admire your ingenuity and it sounds like it looks pretty cool, yet I think you may be putting yourself through unnecessary discomfort.
First,The toppers are, I believe (and Phoenix can correct any errors I make) comfort layers. Meaning, they are not support layers. Your bed almost sounds like a reverse-bed; 10 inches of comfort layers with a three (guessing) inch support layer, instead of a 3-4 inches of comfort layers on top of a 7-8 inch support layer.
Second, you have the latex comfort layers near the bottom. From what I have researched and read, those should be at the top. Latex is fast response compared to memory foam, so I would wonder if lower quality memory foam over latex is not defeating the benefits of it.
Most massage tables are only 26"-30" wide, while the smallest mattresses are 39" wide, which is a twin. If the toppers you purchased are twin, and you did not cut them to size, that would leave quite a few inches of overhang all around the massage table. This creates a “bow-ing” effect; the edges are being pulled down by gravity and their weight, causing the middle to bow up. Then, when you lay down on it, the opposite happens.
When you lay down on it, the edges flare upwards and the middle bows downwards. Unless your massage table is a continous flat surface one, as opposed to, having a pivot point near the center, the effect is compounded. It could further be exacerbated if the table is a folding one. The center becomes a weak link, yet that is where most of the weight falls and needs to be strong.

Additionally, the layers in most mattresses have some kind of adhesion holding the layers together, whether stitched or glued. Sort of like plywood, the individual layers are adhered to make one strong piece. Without that adhesion, the edges would fan, while the middle compresses more than it needs. A simple example you could try at home or the office would be to take a pad of sticky notes and balance it on your fingers. Place the glued side on two fingers and the side without adhesion on your other two fingers. Spread your fingers kind of like the Spock greeting, then press in the middle. You will notice the adhered side moves as one piece, while the other has gaps between the pieces of paper.

You mentioned that your hip/behind area breaks in mattresses harder, yet with your set-up, it would seem that you would feel even more discomfort there. You have the shoulder and foot areas trying to counter-act the mid-section, all while your mid-section and the mattress middle is trying to support the whole thing. Instead of your weight being distributed and supported, small areas are doing too much work.
Also, a massage table does not sound like it leaves you much room to spread out at all. So, along with everything else, your body has to scrunch up some due to width restrictions.
Maybe you think your budget does not allow for a really good mattress, yet I can tell you from personal experience that it does. The big chains, especially, mark up their stuff big time. Many of the family-owned ones do not do it to such a huge margin. I also thought that I would never be able to afford a great mattress for less. Just the other day I purchased a second queen mattress that is soft and supportive, with an added layer of wool and an amazing bamboo top for about half what I paid at a retail outlet for the other.
This is just my opinion, yet I really feel you can have an amazing SET within your budget. It sounds like you are sleeping on less than a twin now, and you could find a regular twin or even a full from one of the manufacturers on the membership page. I recommend you take a look and either call a few, or go to one near you. Maybe you are thinking that they are not as good, or they use cheap materials, but I can tell you from recent (two days ago) experience, that is not the case.
You will still be able to keep your toppers and use them to adjust the comfort, though I would stick with the latex ones and not so much the Walmart foam ones. Finally, a good base mattress will benefit your body. Even a twin would let it relax more, give you room to spread out a bit and lessen the tension.
Hope this helps, and if I made any errors or mistakes, there are a lot of good people on this site who can correct me, and perhaps, expand.