Hi Suzanne, welcome to the glider forums.

First off, if the cage was slimy and disgusting then you did right! Rotten food harbours bacteria and will grow mould and smell especially in the warm weather, it will also attract flies which will lay eggs ... yuk!!!
Get them on to a decent diet, don't worry about the acacia gum, it's a great addition to the diet and does have benefits, but don't worry too much at this stage.
If I were you, I'd leave them alone for a while, moving to a new place is stressful all the new smells and noises etc, don't stress her out more by trying to handle them. Just be passive and speak to them, offer them treats through the bars etc, don't try and handle them yet. A new cage would be a good idea but leave them to settle first. You can minimise stress when you swap cages by putting their cage pouch in so it smells familiar to them. They would probably appreciate the extra space.
It's hard to say when joey will come out of pouch (OOP) as we cannot see how big she is, but if the pouch is stretching and you can actually see the joey, and the joey sticks out a limb or tail then it is likely to come out within the next couple of weeks.
Hope that helped a little as I've got to go back to work now (damn it!).