Terrific. That jar has square sides and you managed to represent that perfectly in spite of the elliptical at the top and bottom. The highlights on the jar and spoon, although subtle, suggest there should be some obvious highlights on the sugar bowl and saucer that I don't see. Maybe it's just me.
Where you put the paint should really be flat and 45degrees to your line of sight otherwise you will get interferences light/reflection/colors. if it is rounded you will find it impossible to light balance your shadow box. You should also cover the whole end of the color checker with a layer of paint that you are matching. If you are looking for an easier and cheaper alternative watch Mark's video on making you own for about 25cents worth of plywood and 10 cents worth of hardware. It's nothing like the one he sells and a 10 year-old could make it. This one you dreamed up could still be made to work and would definitely be easier to hold. Thanks for the ideas.
@tassieguy, as concerns setting up a still life; if you can google images for still-life look for one that has a pleasing composition for you. THEN find some objects of similar size and general shape and arrange them as in the image. It doesn't matter much what they are. an oil can for a tea pot, a baseball for an apple or a triangle of cloth for a vase of tall flowers. colors don't matter much either just paint it to get the ideas to your brain that you are painting from life. That didn't make sense did it?
This is one of those occasions where the artist's skill is driven by inspiration. At least that's what it looks like to me. Tell me @jarube, at any time while painting this did you feel like this was work, tedium or frustration? If the answer is no to all three, then I am right. But if I am wrong you have done an excellent job and can take all the credit.