If the soil is that dry it is possible the yellow leaves are a result of dehydration. Soil should be slightly damp. Dry soil can kill a tree far quicker than wet soil. New bonsai growers are so paranoid about water that I suspect many cases of death that are put down to over watering were probably actually caused by under watering.
If the soil is dry it must be watered, even if that means every day. In summer all my trees get watered every morning and every evening. Air indoors can be quite dry with heating and AC so drying can also be rapid inside.
When you do water it must be enough to thoroughly wet the entire root ball right through to the middle. A little spray is not enough! Soaking the pot in a bucket occasionally is good practice. You may find that when you water properly it will not need water quite as often.
When soil has become dry it can be really hard to wet it again. with poor watering technique the pot gets drier each day despite the watering. Tree finally dies, the beginner blames over watering and the myth continues.
I also want to make sure where I make cuts it'll grow out. A lot of the branches that weap are bare in the middle 4-6 nodes. Plan on cutting them today, where would be a good place to ensure the cuttings grow + the tree still grows?
Chinese elm will grow from almost anywhere. We can chop the trunk and new shoots will grow from the cut end. Light trimming will be no problem. I would normally cut long new shoots so there is only 1 or 2 buds/nodes/leaves left at the base. Even if there are no leaves those nodes can bud and grow new shoots.
At some stacge you will find the tree gets too thick and too bushy. Pruning also means thinning some parts completely so consider pruning some branches growing in the middle right back to the branch or even back to the trunk. none of that will hurt your tree. It will probably actually encourage more growth.
Elm cuttings are generally 3-6" long. Slightly thicker is better as really thin ones may not have enough stored food to grow roots so just throw away any real small pieces.