Re: Need Advice - Disruptive Student
In practicing Aikido we do learn how to manage conflict, so this is another challenge for you. I think you can kick him out. This is a case where "nature abhors a void." Since there is no leadership, this student has stepped in and taken that role.
Since that is apparently how you want to run the dojo, by consensus, then I suggest you meet with the other students, let them know that you would strongly suggest not allowing this student to practice with you any longer for the reasons you have listed. I'm sure your vote counts for a lot, as they are dependent on you and if you're not happy I'm sure that they are not happy. I have a hard time believing that they have not been negatively impacted by this situation.
Now, since conflict resolution is what we learn in Aikido, it would certainly be ideal if you could resolve this situation some other way. Kicking a student out is a drastic measure in my mind and doesn't really solve the problem from coming up another day with a different student.
Have you sat down and spoken to this disruptive student? If he is bothering you then you have I think a mandate to talk to him about what you expect behavior in an Aikido class to be. Weather or not he's being an "Alpha male" is not your concern, just that this class is for you and the students, you are unpaid, and in every class there needs to be rules for yourself and for the students to learn properly. It may not work, but it's a start.
For the purposes of prevention going forward, I suggest giving each new student information on the class and what is expected of them. If would be a good idea to officially register them and take their information so that even though they don't pay, they understand that this is a class and there are expectations for both them and yourself. If you want another student to handle it then they can do it. I think that would help prevent future problems.
I don't know anything about your teaching style, but it might be a good idea to get some feedback from your students on their impression of you as their teacher.