The size I'm looking is approx. 5-6 feet tall...root ball about 1-11/2 ft diameter and 1 ft deep.
Yes, this can be done. You will want to get used to root pruning every three years or so. Since it will need a little extra care in container. This will include pruning thicker anchor roots, while leaving feeder roots. This will keep it happy in container, and keep it from getting rootbound over time.
Keeping in such a small container will only yield a 2 or 3 foot tall tree, though. You may not get the tall tree that you desire from such a small container. It can still survive in these conditions, though.
This article will help: https://www.gardeningknowhow.com/ornamental/trees/japanese-maple/japanese-maples-in-containers.htm
I have a Cercidiphyllum japonicum 'Toffee Apple ina large pot it's about 4 years old. Every year the leaves fall off before they turn yellow and I'm not sure what I do have it in at least 4 hours sunlight in a sheltered part. I not sure if it's the soil which I cant remeber what soil it was though! Any help?
It sounds like it may not receive enough light to be happy. These are full sun shrubs, and will need as much as you can possibly give them. Fortunately, it is pretty easy to provide a little extra light. A florescent fixture will be fine until it is too tall to light well with that sparse of a light.
I recommend at least 200 watts of light for the mature tree. Just stay away from LED panels that are not full spectrum. The red/blue panels will not suffice here.
My personal recommendation on lighting will be a Ceramic Metal Halide (CMH) bulb, and fixture. They are available in a 315 watt fixture that will provide full sunlight to a 4ftx4ft area. This means that anything that, also, needs full sunlight can be lit, as long as it fits in the area.
Here is an article that will give you general information on the tree's care: https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm
I built a deck around my katsura tree 13 years ago. Last year I noticed it seems to be dying, lots of dead limbs high up. This year I saw that some branches started budding then went dead. Can something be done?
Covering the tree roots with a deck could have deprived the tree of moisture and sufficient air circulation. The best thing to put around a tree is mulch to the dripline. You can prune out the damaged limbs and take extra care to see the tree gets its cultural needs. I've included a link to tips for its care. You may want to call an arborist who may be able to save it.
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm
The past 2-3 it’s getting worse
Surface roots are generally not a problem unless they jeopardize nearby structures. Shaving them is not recommended as it can cause instability and allow disease to enter.
Here is more:
https://www.gardeningknowhow.com/ornamental/trees/tgen/exposed-tree-roots.htm
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm
drooped and shrivelled. We have watered it frequently but it seems to be getting worse. This tree is replacing a cherry blossom in memory of my daughter and so it is important it survives. I'm worried.
You might be over-watering your tree. This article will tell you how to fertilize and care for it.
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm
We planted these last year so we’re not sure if this usually happens in the spring.
They require acidic soil and the leaves will turn yellow in alkaline soil. You may want to get your soil tested at least for pH and get that corrected. They also need a mostly shady location.
https://www.gardeningknowhow.com/ornamental/shrubs/japanese-andromeda/grow-japanese-andromeda.htm
I want to plant one next to a man-made stream and pond and I don't want a messy tree that drops fruit or seed pods. Thank you.
They will drop small, banana-shaped pods and will drop their leaves, as well.
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm