Re: "solo" training?
Given your small space you could practice knee walking techniques. I often do weapons when training by myself. If possible I would recommend asking your teacher or senior to allow you to video tape any solo exercises such as kata, suburi, aiki taiso, tai sabaki or whatever similar things are taught in your dojo. That way you can use it as a reference for training when the dojo is closed or you are traveling. I would keep it simple though, you don't want to overburden yourself!