Look into online and LD domination techniques. There is a program called Cybermistress out there which you can set a script for (deciding things like how likely you are to give permission to go to the toilet, eat food, how he dresses and so on) and install on his computer. He keeps it running and it pops up with tasks occasionally, assigns punishments and e-mails you a report. Not as good as being there in person but less work for you in terms of managing his life from a distance

What is your objective with this sub? Do you seriously want to have him in your stable as a non-sexual slave? In which case you could give him tasks to make your life easier - things your regular sub either cannot do or would have trouble doing alone. Get him to do housework, DIY, gardening etc. in exchange for occasional BDSM sessions

However, I suspect your goal is more likely to help him get himself back together after his traumatic break and out there in the market looking for another Domme he can serve in a maybe more sexaul manner. With this in mind, I would consider controlling things like his clothing, his appearance, his diet etc - make him a more attractive prospect for another Domme. However, I would be careful not to alow him to get too attached to you to the extent of considerng you to be his Domme. For one thing, he may not want to find another Domme because, in his mind, he already has one. For another, women in general are very sensitive to 'attached' men and if other Dommes sense that he has a Domme already (however informal) they may be wary of him.