No, if he had a server as well at his house, you would be in one server 'world' and he would be in his own server 'world'. They would not be connected what so ever.
I would guess, given you set him as Admin, he may not be using the correct prefix keyboard character for the commands, or misspelling commands, or you simply did not make his access level Admin like you thought you had. There is something you are overlooking, at any rate.
Again though, not meaning this rude, but you would have much better luck finding answers to this issue on a Sphere forum. There may be some folks here that are familiar with Sphere, but most that have used Sphere around here, was years and years and years ago.. generally speaking.
On the issue about your not having luck starting up a RunUO server, that is something we can certainly help you with. So if you like, let us know what you have done and what did not work for you, and we can absolutely help you get through those troubles.
I would almost start by saying you may not have the correct .Net Framework installed, and for that reason you had errors when you tried to run the RunUO.exe
You would need the .Net Framework version 2.0 / 2.2 for the latest Distro version of RunUO. Future releases of RunUO will require the 4.0 .Net Framework.